Netter's Neurology, 2nd Edition

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Netter’s

Neurology 2nd edition

EDITOR-IN-CHIEF

H. ROYDEN JONES, JR., MD Department of Neurology Lahey Clinic Burlington, Massachusetts; Children’s Hospital Boston Boston, Massachusetts EDITORS

JAYASHRI SRINIVASAN, MD, PhD Department of Neurology Lahey Clinic Burlington, Massachusetts

GREGORY J. ALLAM, MD Department of Neurology Lahey Clinic Burlington, Massachusetts

RICHARD A. BAKER, MD Department of Radiology Lahey Clinic Burlington, Massachusetts

Illustrations by Frank H. Netter, MD CONTRIBUTING ILLUSTRATORS

Carlos A. G. Machado, MD John A. Craig, MD James A. Perkins, MS, MFA Anita Impagliazzo, MA, CMI

1600 John F. Kennedy Blvd. Ste 1800 Philadelphia, PA 19103-2899

NETTER’S NEUROLOGY Copyright © 2012 by Saunders, an imprint of Elsevier Inc.

ISBN: 978-1-4377-0273-6

No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Permissions for Netter Art figures may be sought directly from Elsevier’s Health Science Licensing Department in Philadelphia PA, USA: phone 1-800-523- 649, ext. 3276 or (215) 239-3276; or email [email protected].

Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. With respect to any drug or pharmaceutical products identified, readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of practitioners, relying on their own experience and knowledge of their patients, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. ISBN: 978-1-4377-0273-6

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Dedication

To our dear patients and residents They taught us so much by providing unforgettable life experiences in their own special way. These special encounters continue to bring fond memories, very poignantly motivating each of us. To our wonderful families: spouses, children, and grandchildren with whom we each share a very extraordinary bond

About the Artists

Frank H. Netter, MD Frank Netter was born in 1906 in New York City. He studied art at the Art Student’s League and the National Academy of Design before entering medical school at New York University, where he received his medical degree in 1931. During his student years, Dr. Netter’s notebook sketches attracted the attention of the medical faculty and other physicians, allowing him to augment his income by illustrating articles and textbooks. He continued illustrating as a sideline after establishing a surgical practice in 1933, but he ultimately opted to give up his practice in favor of a full-time commitment to art. After service in the United States Army during World War II, Dr. Netter began his long collaboration with the CIBA Pharmaceutical Company (now Novartis Pharmaceuticals). This 45-year partnership resulted in the production of the extraordinary collection of medical art so familiar to physicians and other medical professionals worldwide. In 2005 Elsevier, Inc., purchased the Netter Collection and all publications from Icon Learning Systems. There are now over 50 publications featuring the art of Dr. Netter available through Elsevier (in the US: www.us.elsevierhealth.com/Netter and outside the US: www.elsevierhealth.com). Dr. Netter’s works are among the finest examples of the use of illustration in the teaching of medical concepts. The 13-book Netter Collection of Medical Illustrations, which includes the greater part of the more than 20,000 paintings created by Dr. Netter, became and remains one of the most famous medical works ever published. The Netter Atlas of Human Anatomy, first published in 1989, presents the anatomical paintings from the Netter Collection. Now translated into 16 languages, it is the anatomy atlas of choice among medical and health professions students the world over.

The Netter illustrations are appreciated not only for their aesthetic qualities, but also, more important, for their intellectual content. As Dr. Netter wrote in 1949, “… clarification of a subject is the aim and goal of illustration. No matter how beautifully painted, how delicately and subtly rendered a subject may be, it is of little value as a medical illustration if it does not serve to make clear some medical point.” Dr. Netter’s planning, conception, point of view, and approach are what inform his paintings and what makes them so intellectually valuable. Frank H. Netter, MD, physician and artist, died in 1991. Learn more about the physician-artist whose work has inspired the Netter Reference collection: http://www.netterimages.com/ artist/netter.htm. Carlos A. G. Machado, MD Carlos Machado was chosen by Novartis to be Dr. Netter’s successor. He continues to be the main artist who contributes to the Netter collection of medical illustrations. Self-taught in medical illustration, cardiologist Carlos Machado has contributed meticulous updates to some of Dr. Netter’s original plates and has created many paintings of his own in the style of Netter as an extension of the Netter collection. Dr. Machado’s photorealistic expertise and his keen insight into the physician-patient relationship informs his vivid and unforgettable visual style. His dedication to researching each topic and subject he paints places him among the premier medical illustrators at work today. Learn more about his background and see more of his art at: http://www.netterimages.com/artist/machado.htm

About the Editors

H. Royden Jones, Jr., MD, was raised in semi-rural New Jersey but also frequently visited his grandmother, who lived a few blocks from the Atlantic Ocean. He graduated from Tufts College and Northwestern University Medical School, where during his first year he was intrigued by the introductory neuroanatomy course, which was particularly enhanced by his use of the first Netter Nervous System atlas and his teacher’s presentation of active patients. Years later as Chair of the Alumni Advisory Board he received their Outstanding Service award. After interning at the Philadelphia General Hospital, Royden began an internal medicine residency at the Mayo Clinic. He completed two years of internal medicine and took his last required rotation, neurology. This unexpectedly rekindled interests that began as a medical student, leading him to make a career shift from cardiology to neurology. One year later he volunteered for active duty, as a neurologist, with the United States Army Medical Corps, serving from 1966 to 1970 at the 5th General Hospital, Bad Cannstatt, Germany. Returning to Mayo, Royden completed his neurologic and clinical neurophysiology training. In 1972 he joined the Lahey Clinic Neurology department, subsequently becoming their Chair and later the Chair of the Division of Medicine and Medical Specialties. Dr. Jones continues to practice at Lahey, where he holds the Jaime Ortiz-Patino chair in neurology. Currently his efforts are entirely dedicated to patient care and educational /clinical research pursuits. Royden is renowned for his astute clinical acumen and his compassionate care of patients. His wisdom is highly sought after by other physicians at Lahey, the surrounding community, as well as nationally. He is recognized as an exceptional teacher and has mentored numerous residents and fellows. His former students practice adult and pediatric neurology across the world. Dr. Jones developed the Lahey neurophysiology fellowship. A number of directors of EMG labs and several department chairs have been trained by Royden. After having joined the Children’s Hospital Boston neurology department, Royden was asked to develop their clinical electromyography laboratory in 1978. This presented an interesting challenge, since there was little written in the field of pediatric electromyography. Keeping careful prospective files of every patient studied there, Dr. Jones subsequently co-authored and edited three major texts of childhood clinical neurophysiology and neuromuscular disorders. Dr. Jones is a Clinical Professor of Neurology at Harvard Medical School and a Lecturer at Tufts University School of Medicine. He served as a Director of the American Board of Psychiatry and Neurology from 1997 to 2004 and concomitantly was a member of the Residency Review Council of the Accreditation Council for Graduate Medical Education. He has served on the editorial boards of Neurology Continuum and Muscle and Nerve and is a reviewer for many neurologic journals. Dr. Jones was the recipient of the Distinguished Physician Award of the American Association of Neuromuscular and

Electrodiagnostic Medicine in 2007 and the Frank Lahey award of the Lahey Clinic Staff Association of 2010. In his free time Royden is a photographer and an amateur sea and landscape artist. He particularly enjoys opportunities to photograph his family, as well as record the magnificence of nature at the 40-mile long Moosehead Lake lying within the mountains of northwestern Maine. Here he spends part of his summer on remote Deer Island with his wife, four children, and five grandchildren. His daughter is a former prosecutor in Manhattan, and one of his sons is a college professor at the University of Rochester. His other two sons are physicians; one practices emergency medicine at a community hospital in suburban Boston, and his youngest son is the A. Bernard Ackerman Professor of the Culture of Medicine conjointly at Harvard College and Harvard Medical School. Their family particularly enjoys skiing, kayaking, and hiking together. Jayashri Srinivasan, MD, PhD, grew up in Chennai, India, where she graduated from Stanley Medical College. She initially pursued her postgraduate training in Cardiff, Wales, where she received a doctorate in neurophysiology, as well as completing a residency in internal medicine and becoming a Fellow of the Royal College of Physicians (FRCP), United Kingdom. Jayashri moved to Boston to train at the Tufts neurology program; subsequently she completed a fellowship in neuromuscular disorders at Brigham & Women’s Hospital and Harvard Medical School. She briefly returned to the Tufts faculty at Tufts Medical Center but soon thereafter moved to the Lahey Clinic in 2003. Jayashri is an associate professor of neurology at Tufts University School of Medicine. At Lahey Dr. Srinivasan specializes in neuromuscular medicine, where she is a very skilful clinical neurophysiologist with particular interests in electromyography and autonomic disorders. She is director of the clinic’s electromyography laboratory, the Lahey neuromuscular fellowship, as well as director of their Muscular Dystrophy Association clinic. Dr. Srinivasan has presented a number of papers at major North American neurologic societies and has written significantly within the neuromuscular field. When she is not practicing neurology, Jayashri devotes almost all of her free time to her family—her husband Bala, a nephrologist at Tufts, and their 2 children, a daughter in college at MIT, and a son in high school. Gregory J. Allam, MD, has a dad and brother who are also physicians. Greg received his medical degree from the American University of Beirut before coming to Boston to pursue his neurology training though the Tufts University program, with additional training in EMG/neuromuscular disease and acute care neurology at the Saint Elizabeth’s Medical Center in Boston. Greg joined the Lahey Clinic neurology department in 1997 as a member of the neurovascular team with interests in critical care neurology, as well as a skillful electromyographer. While at Lahey Greg was recognized as an astute and caring

viii  About the Editors

physician, especially by his many challenging patients whom he followed for their spasticity where his very careful Botox ministrations were often very successful. Dr. Allam recently joined the Brigham and Woman’s Hospital in Boston and is director of stroke care at the South Shore Hospital in South Weymouth, Massachusetts. He is a clinical instructor at the Harvard Medical School and lives in the Suburban Boston area with his wife Christina, an endocrinologist at Children’s Hospital Boston, and their two young children. Richard A. Baker, MD, was raised in rural Ohio and graduated from the College of Wooster and the Case Western Reserve Medical School in Cleveland. He interned at King County Hospital, Seattle, Washington, and began an internal medicine residency there. This was interrupted by service as a physician in the US Air Force. During his military tour Dick was stationed in Greenland, where in addition to his service responsibilities he also volunteered to care for the native Inuits. He then pursued a residency in radiology, initially at the University of Rochester, and then later at the Peter Bent Brigham Hospital in Boston for

another year of radiology followed by a fellowship in neuro­ radiology there and at the Children’s Hospital Boston. After completion of his training, Dr. Baker joined the staff of the Peter Bent Brigham Hospital and Harvard Medical School. The Lahey Clinic recruited him as their first neuroradiologist in 1978. Dick helped to develop this section and later became radiology department chairman, as well as president of the Lahey medical staff. He is currently an Associate Professor of Radiology at Tufts University School of Medicine. His wisdom and clinical acumen are greatly appreciated and highly sought after at Lahey. Dick was a major force in the development of the first volume of Netter’s Nervous System, Part II, Neurologic and Neuromuscular Disorders published in 1986 and the first edition of Netter’s Neurology, published in 2005. Dick has two children, one who followed in the footsteps of her mother as an infectious disease physician at Massachusetts General Hospital and Harvard, and a son who is working on his doctorate. Dr. Baker is a master gardener and a skilled woodworker, something he is pursuing with vigor now that he is working part time. He also enjoys a variety of outdoor activities with his wife, including skiing and hiking.

Acknowledgments

First and foremost I must thank Jaime Ortiz-Patino, my dear friend who underwrote the Jaime Ortiz-Patino Chair in Neuro­ logy at Lahey. This funding has provided me time to devote to this project. Equally important once again, my wonderful wife, Mary, has put up with my very frequent weekend and evening presence behind a laptop computer in our family room. Similarly, Jayashri, Greg, and Dick acknowledge the support and understanding of their families in bringing this project to

completion. My many Lahey Clinic colleagues, in particular Paul T. Gross, MD, our department chairman, have been most gracious in their enthusiastic support of this project. The Elsevier team, including Marybeth Thiel, John Casey, Elyse O’Grady, and Carolyn Kruse, has always been very responsive and gracious in working with us. We are most appreciative of their expertise and support.

Foreword

Neurologic problems are among the most frequent encountered in medicine. The trainee in neurology, whether a medical student or resident, often has difficulty in fully grasping the subject, in part because of the complexities of the anatomy and physiology involved and in part also because of the mystery that still enshrouds the brain. The amazing advances made in the neurosciences over the past quarter century have, on the one hand, helped the clinician in the management of individual patients and, on the other hand, increased wonder about the elegance of cerebral function. The current edition is intended as a resource to aid students endeavoring to understand neuro­ logy and to keep up with advances in the field. Netter’s Neurology was first published in 2005 and met with immediate acceptance. Edited by H. Royden Jones, Jr., a clinical professor of neurology at Harvard Medical School, holder of the Jaime Ortiz-Patino chair in neurology at the Lahey Clinic, and one of the outstanding clinical neurologists of his genera­ tion, the book presented a concise account of the subject, illus­ trated by the renowned medical artwork of Frank Netter and others. Rapid advances in the field have underscored the need for a second edition of the book, however, and it is with especial pleasure that I welcome its publication. The new edition is broader in scope than the earlier one, but improved design and an alteration in trim size have reduced the overall number of pages. Every chapter has been updated and many have been rewritten almost completely to incorporate the accumulated wisdom of recent years and provide more details on treatment. They contain numerous clinical vignettes exem­ plifying important points, such as clues to the site of the lesion,

the features characterizing the typical course of a particular disorder, the investigative approach to clarify the likely diagno­ sis, and the optimal management plan. These vignettes focus the attention of readers on details that might otherwise be over­ looked and help to make the volume clinically relevant, a feature that medical students will find particularly appealing. The artwork, too, has been updated, benefitting from the advances in neuroimaging in recent years. The illustrations, and particu­ larly the rich color plates that made Frank Netter the premier medical artist of his time, help to convey to the reader an under­ standing of clinical neurology and its scientific underpinnings that it is hard to obtain with such facility elsewhere. Dr. H. Royden Jones, the editor, is joined by three co-editors for this new edition. The authors of the individual chapters are drawn from the current or former staff of the Lahey Clinic, and many are former trainees of the senior editor. They are rich in clinical experience, and this is reflected in the text, where a practical approach to the evaluation and management of neuro­ logic disorders is described with enviable clarity. Readers will benefit greatly from this account of clinical neurology with its clear, flowing prose, amplified by the remark­ ably beautiful artwork contained within the volume. Together, the text and artwork will give students a firm grasp of the fun­ damentals of the subject. I congratulate the editors on their achievement in producing such an important addition to the medical literature. Michael J. Aminoff, MD, DSc, FRCP Distinguished Professor of Neurology University of California, San Francisco

Preface

The second edition of Netter’s Neurology speaks to the perpetuity of Frank Netter’s incomparable artistic genius and educational vision. During my first year at Northwestern University Medical School we were forewarned as to how difficult the introductory neuroanatomy course was going to be, “the toughest one” that we would face. A few upperclassmen told me to purchase the Netter Atlas of Neurosciences and it would all fall into place. Indeed it did, and I became interested in a career in neurology. However, in 1960 when I discussed the possibility of a neurologic career with Northwestern’s chairman of their combined psychiatry and neurology department, he told me that one could not make a living as a neurologist; instead I would need to eventually primarily practice Freudian psychiatry while just dabbling in neurology! That was not for me. A few years later my internal medicine residency at Mayo required 3 months of neurology; this was so interesting and intellectually challenging that I switched my career plans to neurology and gave up plans to become a cardiologist. Having continued to be impressed with Dr. Netter’s skillful renditions of many medical subjects, as presented in his semimonthly Ciba Symposia, some years later I enquired at an AMA meeting, where these were on display, as to whether he might have interest in illustrating the various mononeuropathies. Never did I think this suggestion would be transmitted directly to Dr. Netter. However, less than a year later, in 1982, I received a letter from him asking me to elaborate my ideas. I soon found myself visiting Dr. Netter at his new studio in Palm Beach. This was an undreamed of opportunity, especially as one of my hobbies includes rather amateur attempts at oil and water color painting. After a few visits with Frank, who was a very gracious and kind gentleman, he asked me to help him revise his Neurologic and Neuromuscular Disorders of his two-volume Netter Nervous System atlas, the very one that had so impressed me during my first-year neuroanatomy course. We spent many 3-day weekends together as he listened to my ideas as to how best illustrate each subject. The typical Netter day began in his studio at 7 AM … Frank always had a cigar going, and in selfdefense I kept a pipe well stoked. With much help from some dear colleagues, this was published in 1986. We planned to update this text every 6 to 8 years; however, with Frank’s death in 1991 and Ciba Pharmaceutical’s merging into Novartis, ongoing revisions seemed to be relegated to the publishing tundra. Much to my delight in 2000 Icon Publishers contacted me after they had purchased the rights to use the Netter paintings. Their vision led to the development of a number of more traditional, specialty oriented textbooks, and I had the honor of editing the first neurology edition in this more classic format. Now 52 years after my introduction to Dr. Netter’s artwork, we are finishing my third text utilizing his magnificent paintings and are already proceeding to a new edition of his Neurosciences atlas. On this occasion I have asked three colleagues to co-edit this volume with me. My dear friend, Richard Baker, a highly

esteemed clinical neuroradiologist, has provided the neuroradiologic images for both of our earlier Netter texts. Concomitantly I recruited two outstanding younger Lahey colleagues, Jayashri Srinivasan and Gregory Allam, as our other co-editors. Both are master clinicians who are highly respected for their clinical acumen and teaching abilities. It has been an honor to work with both of them for more than a decade. As with the first edition of Netter’s Neurology all of the authors have a Lahey Clinic heritage either as a current staff member, a former fellow, or former staff. This seemingly parochial approach has allowed us to minimize duplication and, more important, ensure the reader that what is discussed herein represents the latest approach to the patient with a clinical neurologic problem. As Frank Netter often stated to me “a picture is worth a thousand words.” Indeed they are, and his magnificent plates provide the foundation for this monograph. However, when conceiving the overall format for the first edition of Netter’s Neurology it was very important for me not only to include an overview of a neurologic condition but also to use clinical case vignettes, particularly since these are my most effective means of teaching. Case-based methodologies are currently used at a number of medical schools; we have aimed this volume to complement such for both the undergraduate medical student as well as residents. My first neuroscience teachers at Northwestern very effectively used patient presentations to bring life to the complexities of basic neurologic anatomy and physiology. This didactic approach was very well received by the beginning student and resident alike in the first edition of Netter’s Neurology. We also think that the practicing clinical neurologist will find this combination of basic anatomy and clinical neurology to be a refreshing alternative to the various forms of clinical review now available for our required recertification process. Concomitantly my co-editors and I hope that the internal medical resident and the general internist will find the blending of Netter paintings with clinical medicine to be similarly useful. Every chapter in this second edition has been carefully reviewed and in most instances significantly rewritten. The total number of chapters was reduced, as we combined some subjects into one broader area. Many new vignettes have been added, and in a number of instances we replaced some of those in the first edition. The plates have a number of new MR images, and some are reedited in their entirety. New plates have also been added. Elsevier has changed the overall format to a standard text size that provides a slimmer volume. As in the first edition this is not a source for specific pharmacologic dosing, as such is an ever evolving standard. We are excited to be able to present this volume and are particularly pleased to be able to take advantage of the many publishing attributes that the Elsevier/Saunders staff brings to the table. H. Royden Jones, Jr., MD June 5, 2011

Contributors

Lloyd M. Alderson, MD Department of Neurosurgery Lahey Clinic Burlington, Massachusetts Timothy D. Anderson, MD Department of Otolaryngology Lahey Clinic Burlington, Massachusetts Diana Apetauerova, MD Department of Neurology Lahey Clinic Burlington, Massachusetts Jeffrey E. Arle, MD, PhD Department of Neurosurgery Lahey Clinic Burlington, Massachusetts Ritu Bagla Department of Neurology Lahey Clinic Burlington, Massachusetts Ted M. Burns, MD University of Virginia Health Sciences Department of Neurology Charlottesville, Virginia Ann Camac, MD Department of Neurology Lahey Clinic Lexington, Massachusetts Peter J. Catalano, MD Department of Otolaryngology Lahey Clinic Burlington, Massachusetts Claudia J. Chaves, MD Department of Neurology Lahey Clinic Lexington, Massachusetts Ellen Choi, MD Attending Anesthesiologist Santa Clara Valley Medical Center San Jose, California

G. Rees Cosgrove, MD Professor and Chairman Department of Neurosurgery Brown University Medical School Providence, Rhode Island Donald E. Craven, MD Chairman, Department of Infectious Diseases Lahey Clinic Burlington, Massachusetts; Professor of Medicine Tufts University School of Medicine Boston, Massachusetts Carlos A. David, MD Department of Neurosurgery Lahey Clinic Burlington, Massachusetts Peter K. Dempsey, MD Department of Neurosurgery Lahey Clinic Burlington, Massachusetts Robert A. Duncan, MD Department of Infectious Diseases Lahey Clinic Burlington, Massachusetts Stephen R. Freidberg, MD Department of Neurosurgery Lahey Clinic Burlington, Massachusetts Paul T. Gross, MD Chairman, Department of Neurology Lahey Clinic Burlington, Massachusetts Jose A. Gutrecht Department of Neurology Lahey Clinic Burlington, Massachusetts Gisela Held, MD Department of Neurology Lahey Clinic Northshore Peabody, Massachusetts Doreen Ho Department of Neurology Lahey Clinic Burlington, Massachusetts



Kinan K. Hreib, MD, PhD Department of Neurology Lahey Clinic Burlington, Massachusetts Allison Gudis Jackson, MS, CCC-SLP Greenwich, Connecticut Samuel E. Kalluvya, MD Bugando Medical Centre Mwanza, Tanzania Johannes B. Kataraihya, MD Bugando Medical Centre Mwanza, Tanzania Kenneth Lakritz, MD Department of Psychiatry Lahey Clinic Burlington, Massachusetts Julie Leegwater-Kim, MD, PhD Department of Neurology Lahey Clinic Burlington, Massachusetts Juliana Lockman University of Virginia Health Sciences Department of Neurology Charlottesville, Virginia Marie C. Lucey Clinical Director Gorden College Center for Balance, Mobility, and Wellness Wenham, Massachusetts Caitlin Macaulay, PhD Department of Neurology Lahey Clinic Burlington, Massachusetts Subu N. Magge, MD Department of Neurosurgery Lahey Clinic Burlington, Massachusetts John Markman, MD Departments of Neurology and Anesthesiology Lahey Clinic Burlington, Massachusetts Ippolit C. A. Matjucha, MD Former Neuro-ophthalmologist Lahey Clinic Burlington, Massachusetts

Contributors  xiii

Michelle Mauermann Consultant in Neurology Assistant Professor of Neurology Mayo Clinic Rochester, Minnesota Daniel P. McQuillen, MD Department of Infectious Diseases Lahey Clinic Burlington, Massachusetts Eva M. Michalakis, MS Department of Otolaryngology Lahey Clinic Burlington, Massachusetts Carol Moheban, MD Lahey Clinic Northshore Mary Anne Muriello, MD Department of Neurology Lahey Clinic Burlington, Massachusetts Winnie W. Ooi Department of Infectious Diseases Lahey Clinic Burlington, Massachusetts Joel M. Oster, MD Department of Neurology Lahey Clinic Burlington, Massachusetts E. Prather Palmer, MD Emeritus Staff Department of Neurology Lahey Clinic Burlington, Massachusetts Robert Peck, MD Bugando Medical Centre Mwanza, Tanzania Dana Penney, MD Department of Neurology Lahey Clinic Burlington, Massachusetts James A. Russell, DO Department of Neurology Lahey Clinic Burlington, Massachusetts Monique M. Ryan, MB BS, M Med, FRACP Royal Children’s Hospital Murdoch Children’s Research Institute Melbourne Australia

xiv  Contributors

Clemens M. Schirmer Director of Cerebrovascular and Endovascular Neurosurgery Baystate Medical Center Assistant Professor Department of Neurosurgery Tufts University School of Medicine Boston, Massachusetts Miruna Segarceanu, MD Department of Neurology Dartmouth-Hitchcock Clinic Manchester, New Hampshire Matthew Tilem, MD Department of Neurology Lahey Clinic Burlington, Massachusetts Michal Vytopil, MD Department of Neurology Lahey Clinic Burlington, Massachusetts

Judith White, MD Head, Section of Vestibular and Balance Disorders Head and Neck Institute Cleveland Clinic Cleveland, Ohio Yuval Zabar, MD Department of Neurology Lahey Clinic Burlington, Massachusetts Isabel A. Zacharias, MD Transplant Department Lahey Clinic Burlington, Massachusetts

Clinical Neurologic Evaluation H. Royden Jones, Jr., and Kinan Hreib

T

he neurologic sciences are the most intellectually challenging, unequivocally fascinating, and tremendously stimulating of the various clinical disciplines. Initially, the vast intricacies of basic neuroanatomy and neurophysiology often seem overwhelming to both medical student and neuroscience resident alike. However, eventually the various portions of this immense knowledge base come together in a discernible pattern, not unlike a Seurat canvas. Often one is expanding or revisiting our neurologic base as we are challenged by variations on the theme of our previous experiences. It is the keen observation and coding of these clinical experiences that leads the astute neurologic physician to solve new patient challenges. One must first and foremost be an astute historian initially listening very carefully to the patient. Most often the intricacies, as well as the subtleties, of the neurologic history provide the essential foundation leading to a rational and structured neurologic examination as well as the appropriate diagnostic testing. Although it is easy to define the requisite methodology to examine the neurologic patient, it is much more challenging to similarly address the history acquisition other than making a few generalities. One of the most important elements of neurologic training is the opportunity for the student and the resident to observe senior neurologists evaluate a patient. As a resident, this was absolutely one of our most important learning experiences. Too often the student does not appreciate the elegance illustrated by a carefully derived neurologic clinical history. A major attribute of a skillful and successful neurologist is being an astute listener. This requires the neurologist to bring together various seemingly disparate and subtle data from the patient’s various concerns and then focus on this information with specific questions to decide on its relevance to the issues at hand. Understanding the temporal profile of the patient’s symptoms is crucial; were the symptoms’ onset acute and stable or have they followed an ingravescent course? Very often, this information provides a most important perspective that is one of the very important keys to diagnosis.

Clinical Vignette A 42-year-old woman with juvenile autoimmune diabetes mellitus came for further investigation of her extremely painful neuropathy initially presumed secondary to diabetes, or possibly to recent chemotherapy for breast cancer. However, her temporal profile was the final clue to her diagnosis. On careful review of the onset of her symptoms, it was found that she had never had the slightest hint of intolerable paresthesiae until awakening from her mastectomy. Her pain had begun precipitously in the recovery room. It was steady from its inception and totally incapacitating in this previously vigorous woman whose favorite pastime was backpacking in mountainous national forests. This temporal profile was in total contradistinction to any

1 

symmetric diabetic or antineoplastic chemotherapy-related polyneuropathy. These disorders always have a clinical course of a subtle onset and very gradual evolution. With this information, we investigated what transpired at the time of her breast surgery when she awakened with this extremely limiting painful neuropathy. In fact, she had had a general anesthetic with nitrous oxide (N2O) induction. This N2O uncovered a second autoimmune disorder, namely vitamin B12 deficiency. The anesthetic had precipitously led to symptoms in this previously clinically silent process. Fortunately, vitamin B12 replacement led to total resolution of her symptoms. Comment: In this instance, her initial physicians had let themselves be trapped by what was familiar to them because diabetes is the most common cause for a painful neuropathy. However, only rarely does it lead to a precipitous onset of symptoms. The fine-tuning of this patient’s temporal profile, especially the abrupt onset of symptoms, led us to seek a more detailed history as to whether some toxic process was operative. Review of the operative records per se led to the diagnosis when the suspicion of nitrous oxide intoxication was confirmed.

Most neurologic disorders follow a well-defined clinical paradigm. However, it is their very broad clinical perspective that continually challenges the astute neurologic clinician to maintain a vigilant intellectual posture. When these specific clinical subtleties are appreciated, the clinician is rewarded with the knowledge of having done the very best for his or her patient as well as having the intellectual rewards for being on the cutting edge of the clinical neurosciences. The skillful clinician, taking a very careful history, is the one most able to recognize the attributes of something quite uncommon presenting in a fashion more easily confused with more mundane afflictions. For example, numbness or tingling in a patient’s hand most commonly represents entrapment of the median nerve at the wrist, reflecting the presence of a very common disorder known as the carpal tunnel syndrome. However symptoms of this type may occasionally represent early signs of a pathologic lesion at the level of the brachial plexus, nerve root, spinal cord, or brain per se. It is imperative for the clinician to always consider a broad anatomic perspective in each patient evaluation. When this approach is not carefully followed, less common, and potentially treatable disorders may not be diagnosed in a timely fashion. It is absolutely imperative that no compromise be made in obtaining a thorough and accurate history when first meeting the patient. This is the most important interchange the physician will have. It needs to be taken in a relaxed, hopefully noninterrupted setting allowing for privacy. Additionally, it is very important to invite the spouse, parent, or significant other into the room. Rarely will a patient object to same; having another close



observer of a patient’s difficulties available can provide insight that may be essential to diagnosis. A thorough initial evaluation engenders a patient-family sense of trust in the physician as a detailed history, with a careful examination demonstrates a major commitment. Once developed, this clinical setting encourages the patient to communicate openly with their physician as they outline their diagnostic plans and eventually a treatment formulation. This chapter provides a foundation that will serve as an anchor for both the student and resident as they learn the art and science of the performance of detailed neurologic evaluations.

NEUROLOGIC HISTORY AND EXAMINATION An accurate history requires paying attention to detail, often observing the patient’s demeanor while reading the patient’s body language, having the opportunity to witness the patient’s difficulties, and interviewing family members. History taking is a special art and science in its own right. It is a skill that requires ongoing additions to one’s own interviewing techniques. Listening to the patient is a most important part of this exercise; it is something that can be more time consuming than current clinical practice “time allowed guidelines” provide for within various patient settings. This approach provides the diagnostic keystone that often distinguishes an astute clinician’s ability to find a diagnosis where others have failed. A complete neurologic examination also requires carefully honed acquired skills. For example, the ability to decide whether the patient is truly weak and not giving way, or similarly does or does not have a Babinski sign present, often makes the difference between arriving at a correct diagnosis. The ability to define a sensory loss at a spinal cord level is another very crucial exercise. One of the most challenging clinical scenarios occurs with the patient who has already seen another clinical neurologist and no diagnosis has been made. The patient is frustrated, as often was his or her prior neurologist. To be fair to the patient, as well as oneself, when evaluating such an individual seeking another neurologic opinion it is important to gain one’s own initial and totally unbiased history and examination. Furthermore, in order to prevent unwelcome bias, the new neurologist should avoid reading other colleagues’ notes or looking at previous neurologic images prior to gaining his or her own history and performing the examinations. Although time-consuming, the history is the most important factor leading to accurate diagnoses. One of the essential attributes of a skillful neurologist is the ability to be a good listener so as not to miss crucial historic points. It is important to begin the initial meeting by asking patients why they have come; this offers them the opportunity to express concerns in their own words. If at all possible, the neurologist should not interrupt, thus providing the patient the opportunity to provide their primary concerns to the neurologist, emphasizing the symptoms of greatest importance. Rarely, anxious or compulsive patients may speak of their concerns at great length; with experience, physicians learn to make discreet interjections to maintain control of the evaluation and draw the patient back from extraneous tangents.

CHAPTER 1  •  Clinical Neurologic Evaluation  3

When the patient’s primary concerns are established, specific issues can be explored. Additionally, making careful observations during the review of history allows better focus for subsequent questions. An accurate baseline assessment of mental status and language can be obtained from listening to the patient and observing responses to questions. It is through listening that the clinician gains insight into the patient’s real concerns. For example, it is not unusual to see a patient referred to a neurologist for evaluation of headaches, which only became exacerbated with the recent discovery of a brain tumor in someone known to the patient. Unfortunately, the economics of modern health care has forced primary care physicians and specialists to shorten visit times with patients and their families. One must be fastidious not to use diagnostic tools, such as magnetic resonance imaging (MRI), as substitutes for careful clinical history and examination. The current detailed medical information available on the Internet, in conjunction with a more sophisticated basic health education environment, has indeed enhanced patients’ knowledge bases, although not always in a balanced format. Patient expectations sometimes affect the diagnostic approach of physicians. In this environment, it is not surprising that imaging techniques such as MRI and computed tomography (CT) have replaced or supplemented a significant portion of clinical judgment. However, even the most dramatic test findings may prove irrelevant without appropriate clinical correlation. To have patients unnecessarily undergo surgery because of MRI findings that have no relation to their complaints may lead to a tragic outcome. Therein lies the importance of gaining a complete understanding of the clinical issues. Although neurology may seem in danger of being subsumed by overreliance on highly sophisticated diagnostic studies, this needs to be kept in perspective as many of these innovations have greatly improved our diagnostic skills and therapeutic capacities. For example, much knowledge regarding the early recognition, progression, and response to treatment of multiple sclerosis (MS) depends on careful MRI imaging. It is essential to make patients feel comfortable in the office, particularly by fostering a positive interpersonal relationship. Taking time to ask about patients’ lives, education, and social habits often provides useful clues. A careful set of questions providing a general review of systems may lead to the key diagnostic clue that focuses the evaluation. When the patient develops a sense of confidence and rapport with an empathetic physician, he or she is more willing to return for follow-up, even if a diagnosis is not made at the initial evaluation. Sometimes a careful second or third examination reveals a crucial historic or examination difference that leads to a specific diagnosis. Follow-up visits also allow the patient and physician to have another conversation regarding the symptoms and concerns. Some patients may come to their first office visit with an exhaustive list of concerns and symptoms, whereas others provide minimal information. Subsequent visits are therefore intended not only to discuss the results of tests but also to clarify the symptoms and or response to treatment. If patients feel rushed on their first visit, they may not return for follow-up, thus denying the neurologist a chance at crucial diagnostic observations. The physician–patient relationship must always be carefully nurtured and highly respected.

4  SECTION I  •  Initial Clinical Evaluation

APPROACH TO THE NEUROLOGIC EVALUATION Throughout training, examination skills are continually being amplified as the resident is exposed to an ever-evolving clinical experience. One of the most important is the opportunity to observe the varied skill sets demonstrated by academic neuro­ logists as they approach different types of patients. One of the essentials for appropriate interpretation of the neurologic patient evaluation is learning how to elicit important, sometimes subtle, clues to diagnosis; an appreciation of what is “normal” at different ages is also important. A hasty history and examination can be misleading. For example, briskly preserved ankle reflexes in an elderly patient is not normal, whereas moderately diminished vibration sense is normal at the ankles. For example, a diagnosis of early MS may be missed by not asking about such things as previous problems with visual function, shooting electric paresthesiae when bending the neck (Lhermitte sign), or sphincter problems manifested by increasing urgency to urinate. Even though carpal tunnel syndrome is the most common cause for a patient to experience a numb hand, one must always be fastidious not to overlook other potential pathoanatomic sites, such as within the peripheral nervous system at the level of the more proximal median nerve, the brachial plexus, or the cervical nerve root. In another instance, the failure to undress a patient whom one suspects to have a pre­ sumably benign cause for a numb hand, that is, carpal tunnel syndrome, may preclude the examining physician from recognizing the presence of an unexpected positive Babinski response indicative of a central nervous system (CNS) lesion. Similarly, identifying a sensory level is indicative of a myelopathy as the pathophysiologic explanation for the patient’s numb hand. Lastly the finding that the sensory loss in the fingers primarily involves position sense and stereognosis becomes the entre to examine the cerebral cortex as the site for these complaints. Another important outcome from performing a complete neurologic examination at the initial evaluation in almost every patient is that this not only establishes the patient’s current status but will provide a baseline for future comparison. There are certain “normal” asymmetries in many individuals, often not previously appreciated by the patient per se or his or her relatives. These may include a patient’s slightly asymmetric smile, somewhat irregular pupils, or hint of ptosis. However, at times such findings do take on significant meaning. As an example, a middle-aged woman was thought to have benign tension headaches. This was based on a “normal” neurologic exam elsewhere. However she had an asymmetric smile that previously had not been appreciated. Imaging studies identified a frontal lobe tumor contralateral to her weakness. Thus, the careful observation of seemingly subtle clinical findings may prove to have significant bearing on the issue at hand. Even when these findings are proven to be “normal variants,” clear documentation may often be very helpful during the course of the patient’s illness or later on when new concerns occur. In that setting, the prior definition of what proves to be a normal asymmetry will prevent erroneous conclusions from being developed.

Formulation One of the most intellectually challenging aspects of neurology relates to the neurologist’s ability to amalgamate the historical and physical findings into a unitary hypothesis. One needs to first consider the multiple neuroanatomic sites that can potentially explain the patient’s clinical presentation. Subsequently, this is placed in the perspective of the clinical temporal profile of symptom occurrence. Did all of the patient’s symptoms begin abruptly, as usually seen with a stroke but sometimes with a tumor or demyelinating process? Or was there an evolution of degree of clinical loss or did new features gradually get added to the patient’s findings as is characteristic of certain neoplastic lesions and sometimes more diffuse vasculitides. Formulation can be hindered by the patient’s inability to provide an accurate history or participate in the neurologic examination. One of the more subtle and difficult conditions to recognize is anosognosia to one’s illness, as may occur in patients with right parietal brain injury. Under these circumstances, the patient may not have sensory, visual, or motor neglect, but unawareness of cognitive, emotional, and other functional limitations. Family interview is most important in this setting.

Overview and Basic Tenets The neurologic examination begins the moment the patients get out of their seat to be greeted, the character of their smile or lack thereof, and subsequently as they walk to enter the neurologist’s office. An excellent opportunity to judge the pati­ ent’s language function and cognitive abilities occurs during the acquisition of the patient’s history. Concurrently, the neurologist is always attuned to carefully making observations in order to identify various clinical signs. Some are overt movements (tremors, restlessness, dystonia or dyskinesia); others are subtler, e.g., vitiligo, implying a potential for a neurologic autoimmune disorder. Equally important may be the lack of normal movements, as seen in patients with Parkinson disease. By the time the neurologist completes the examination, she or he must be able to categorize and organize these historical and examination findings into a carefully structured diagnostic formulation. The subsequent definition of the formal examination may be subdivided into a few major sections. Speech and language are assessed during the history taking. The cognitive part of the examination is often clearly defined with the initial history and often does not require formal mental status testing. However there are a number of clinical neurologic settings where this evaluation is very time consuming and complicated; Chapter 2 is dedicated to this aspect of the patient evaluation. However, when there is no clinical suspicion of either a cognitive or language dysfunction, these more formal testing modalities are not specifically required. Here the multisystem neurologic examination provides a careful basis for most essential clinical evaluations. Neurologists in training and their colleagues in practice cannot expect to test all possible cognitive elements in each patient that they evaluate. Certain basic elements are required; most of these are readily observable or elicited during initial clinical evaluation. These include documentation of language function, affect,



CHAPTER 1  •  Clinical Neurologic Evaluation  5

II Optic

I Olfactory

III Oculomotor (all eye muscles except superior oblique and lateral rectus; also ciliary, iris, sphincter)

V Trigeminal Sensory to face sinuses, teeth, etc IV Trochlear Superior oblique

VI Abducent Lateral rectus

.

hth

Op

Motor to muscles of mastication

x.

Ma

nd.

Ma

Intermediate nerve Motor—submandibular, sublingual, lacrimal glands. Taste—anterior 2⁄3 of the tongue and soft palate. Sensory—external auditory meatus and nasopharynx.

VII Facial Muscles of face and stapeduis

VIII Vestibulocochlear Cochlear

Vestibular

IX Glossopharyngeal Taste—posterior 1⁄3 of tongue. Sensory—tonsils, pharynx, middle ear, and soft palate Motor—stylopharyngeus, pharyngeal musculature

X Vagus Motor—pharynx, heart, lungs, bronchi, GI tract. Sensory—heart, lungs, bronchi, trachea, larynx, pharynx, GI tract, external ear

XII Hypoglossal Tongue muscles Strap muscles (amsa cervicalis)

XI Accessory Sternocleidomastoid, trapezius

Motor fibers Sensory fibers

Figure 1-1  Cranial Nerves: Distribution of Motor and Sensory Fibers.

concentration, orientation, and memory. When concerned about the patient’s cognitive abilities, the neurologist must elicit evidence of an apraxia or agnosia and test organizational skills. Once language and cognitive functions are assessed, the neurologist dedicates the remaining portion of the exam to the examination of many functions. These include visual fields, cranial nerves (CNs) (Fig. 1-1), muscle strength, muscle stretch reflexes (MSRs), plantar stimulation, coordination, gait and equilibrium, as well as sensory modalities. These should routinely be examined in an organized rote fashion in order not to overlook an important part of the examination. The patient’s general health, nutritional status, and cardiac function, including the presence or absence of significant arrhythmia, heart murmur, hypertension, or signs of congestive failure, should be noted. If the patient is encephalopathic, it is important to search for subtle signs of infectious, hepatic, renal, or pulmonary disease.

CRANIAL NERVES: AN INTRODUCTION The 12 CNs subserve multiple types of neurologic function (see Fig. 1-1). The cranial nerves are formed by afferent sensory fibers, motor efferent fibers, or mixed fibers traveling to and from brainstem nuclei (Fig. 1-2A and B). The special senses are represented by all or part of the function of five different CNs, namely, olfaction, the olfactory (I); vision, the optic (II); taste, the facial (VII) as well as the glossopharyngeal (IX); hearing as well as vestibular function, the cochlear and vestibular (VIII) nerves. Another three CNs are directly responsible for the coordinated, synchronous, and complex movements of both eyes; these include CNs III (oculomotor), IV (trochlear), and VI (abducens). Cranial nerve VII is the primary CN responsible for facial expression, which is important for setting the outward signs of the patient’s psyche’s representation to his family and close associates, or signs of

6  SECTION I  •  Initial Clinical Evaluation

Oculomotor (III) n. Red nucleus Accessory oculomotor (Edinger-Westphal) nucleus Oculomotor nucleus Trochlear nucleus Trochlear (IV) n.

Superior (cranial) colliculus Relay centers for fibers in optic tract Lateral geniculate body Mesencephalic nucleus of trigeminal n. Trigeminal (V) n. and ganglion Principal (pontine) sensory nucleus of trigeminal n. Facial (VII) n. Vestibulocochlear (VIII) n. Ventral cochlear nucleus Dorsal cochlear nucleus Vestibular nuclei Glossopharyngeal (IX) n. Vagus (X) n. Spinal tract and spinal nucleus of trigeminal n. Solitary tract nucleus Dorsal vagal nucleus Gracile nucleus

Trigeminal (V) n. and ganglion Motor nucleus of trigeminal n. Abducent nucleus Geniculate ganglion of facial n. Facial nucleus Superior and inferior salivatory nuclei Nucleus ambiguus Dorsal vagal nucleus Glossopharyngeal (IX) n. Hypoglossal nucleus Vagus (X) n. Accessory (XI) n. Spinal nucleus of accessory n.

Viewed in Phantom from Behind

Red nucleus Oculomotor (III) n. Mesencephalic nucleus of trigeminal n. Trigeminal (V) n. and ganglion Principal (pontine) sensory nucleus of trigeminal n. Motor nucleus of trigeminal n. Spinal tract and spinal nucleus of trigeminal n. Facial (VII) n. Vestibulocochlear (VIII) n. Abducent (VI) n.

Efferent fibers Afferent fibers Mixed fibers

Glossopharyngeal (IX) n. Hypoglossal (XII) n. Vagus (X) n. Accessory (XI) n. Spinal nucleus of accessory n.

Accessory oculomotor (Edinger-Westphal) nucleus Oculomotor nucleus Trochlear nucleus Trochlear (IV) n. Abducent nucleus Facial nerve loop Facial nucleus Vestibular nuclei Ventral and dorsal cochlear nuclei Superior and inferior salivatory nuclei Solitary tract nucleus Dorsal vagal nucleus Hypoglossal nucleus Nucleus ambiguus

Viewed in Lateral Dissection

Figure 1-2  Cranial Nerves: Nerves and Nuclei.

paralysis from a brain or cranial nerve lesion. Facial sensation is subserved primarily by the trigeminal nerve (V); however, it is a mixed nerve also providing primary motor contributions to mastication. The ability to eat and drink depends on CNs IX (glossopharyngeal), X (vagus), and XII (hypoglossal). The hypoglossal and recurrent laryngeal nerves are also important to the mechanical function of speech. Last, CN-XI, the accessory, contains both cranial and spinal nerve roots that provide motor innervation to the large muscles of the neck and shoulder. Disorders of the CNs can be confined to a single nerve such as the olfactory (from a closed-head injury, early Parkinson disease, or meningioma), trigeminal (tic douloureux), facial (Bell palsy), acoustic (schwannoma), and hypoglossal (carotid dissection). There is a subset of systemic disorders with the potential to infiltrate or seed the base of the brain and the brainstem at the points of exit of the various CNs from their intraaxial origins. These processes include leptomeningeal seeding of

metastatic malignancies originating in the lung, breast, and stomach, as well as various lymphomas, or granulomatous processes such as sarcoidosis or tuberculosis, each leading to a clinical picture of multiple, sometimes disparate cranial neuropathies. Many times, a stuttering onset occurs. The various symptoms are related to individual CNs. These typically develop within just weeks or no more than a few months. Cranial nerve dysfunctions will commonly bring patients to medical attention for a number of clinical limitations. These include ophthalmic difficulties, such as diminished visual acuity or visual field deficits (optic nerve and peri-cavernous chiasm) and double vision, either horizontal, vertical, or skewed (oculomotor, trochlear, and abducens nerves). Other cranial nerve presentations include facial pain (trigeminal nerve), evolving facial weakness (facial nerve), difficulty swallowing (glossopharyngeal and vagus nerves), and slurred speech (hypoglossal nerves).



CHAPTER 1  •  Clinical Neurologic Evaluation  7

CRANIAL NERVE TESTING I: Olfactory Nerve The sense of smell is a very important primordial function that is much more finely tuned in other animal species. Here other mammals are able to seek out food, find their mates, and identify friend and foe alike because of their finely tuned olfactory brain. In the human, the loss of this function can still occasionally have very significant consequences primarily bearing on personal safety. If the human being cannot smell fires or burning food, their survival can be put at serious risk. The loss of smell also affects the pleasure of being able to taste, even though, as later noted, taste per se is primarily a function of cranial nerves VII and IX. Olfactory nerve function testing is relevant despite its only occasional clinical involvement. This may be impaired after relatively uncomplicated head trauma and in individuals with various causes of frontal lobe dysfunction, especially an olfactory groove meningioma. Loss of olfaction is sometimes an early sign of Parkinson disease. Clinical evaluation of olfactory functions is straightforward. The examiner has the patient sniff and attempt to identify familiar substances having specific odors (coffee beans, leaves of peppermint, lemon). Inability or reduced capacity to detect an odor is known as anosmia or hyposmia, respectively; inability to identify an odor correctly or smell distortion is described as parosmia or dysosmia. Bilateral olfactory nerve disturbance with total loss of smell, typically from

head trauma, chronic upper airway infections, or medication, is usually a less ominous sign than unilateral loss, which raises the concern for a focal infiltrative or compressive lesion such as a frontal grove meningioma.

II: Optic Nerve Of all the human sensations, the ability to see one’s family and friends, to read, and appreciate the beauties of nature, it is difficult to imagine life without vision, something that is totally dependent on the second cranial nerve. Obviously many individuals, such as Helen Keller, have vigorously and successfully conquered the challenge of being blind; however, given the choice, vision is one of the most precious of all animal sensations. “Blurred” vision is a common but relatively nonspecific symptom that may relate to dysfunction anywhere along the visual pathway (Fig. 1-3). When examining optic nerve function, it is important to identify any concomitant ocular abnormalities such as proptosis, ptosis, scleral injection (congestion), tenderness, bruits, and pupillary changes. Visual acuity is screened using a standard Snellen vision chart that is held 14 inches from the eye. Screening must be performed in proper light as well as to the patient’s refractive advantage using corrective lenses or a pinhole when indicated. A careful visual field evaluation is the other important means to assess visual function. These tests are complementary, one testing central resolution at the retinal level and the other to

Central darker circle represents macular zone. Overlapping visual fields

Lightest shades represent monocular fields. Each quadrant is a different color.

Projection on left retina

Projection on right retina Optic (II) nerves Optic chiasm

Projection on left dorsal lateral geniculate nucleus Ipsilateral

Meyer loop

6 5 4 3 2 1

Contralateral

Projection on left occipital lobe

Calcarine fissure

Figure 1-3  Visual Pathways: Retina to Occipital Cortex.

Optic tracts Lateral geniculate bodies

Meyer loop

Projection on right dorsal lateral geniculate nucleus Ipsilateral 6 5 4 3 2 1

Contralateral

Projection on right occipital lobe

8  SECTION I  •  Initial Clinical Evaluation

geographic shape mimics the oblique teardrop shape of aviatorstyle sunglass lenses. In static perimetry, the test point is not moved, but turned on in a specific location. Typically automated, computer testing preselects locations within the central 30° of field. Stimuli are dimmed until they are detected only intermittently on repetitive presentation—this intensity level is called the threshold. The computer then generates a map of numeric values of the illumination level required at every test spot, or the inverse of this level, often called a sensitivity value. Values may also be displayed as a grayscale map, and statistical calculations can be performed—by comparing to adjacent spots or precalculated normal values or noting sudden changes in sensitivity—to detect abnormal areas. Most visual field changes have localizing value: specific location of the loss, its shape, border sharpness (i.e., how quickly across the field the values change from abnormal to normal). Its concordance with the visual field of the other eye tends to implicate specific areas of the visual system. Localization is possible because details of anatomic organization at different levels predispose to particular types of loss (see Chapter 4). When one examines the pupils, their shape and size need to be recorded. A side-to-side difference of no more than 1 mm in otherwise round pupils is acceptable as a normal variant. Pupillary responses are tested with a bright flashlight and are primarily mediated by the autonomic innervation of the eye (Fig. 1-4). A normal pupil reacts to light stimulus by constricting with the

evaluate peripheral visual field defects secondary to lesions at the levels of the optic chiasm, optic tracts, and occipital cortex. Visual fields are evaluated by having the patient sit comfortably facing the examiner at a similar eye level. First, each eye is tested independently. The patient is asked to look straight at the examiner’s nose. The examiner extends an arm laterally, equidistant from himself and the patient, and asks the patient to differentiate between one and two fingers. The patient’s attention must always be directed back to the examiner as most patients will reflexively look laterally at the fingers. This will require repeated testing. Each quadrant of vision is evaluated separately. After individual testing, both eyes are tested simultaneously for visual neglect, as may occur with right hemispheric lesions. Progressively complex perimetric devices have the advantage of providing valuable data on the health of the visual system. In kinetic perimetry, a stimulus is moved from a non-seeing area (far periphery or physiologic blind spot) to a seeing area, with patients indicating at what point the stimulus is first noticed. Testing is repeated from different directions until a curve can be drawn connecting the points at which a given stimulus is seen from all directions. This curve is the isopter for that stimulus for that eye. The isopter plot has been likened to a contour map, showing “the island of vision in a sea of darkness.” The Goldmann perimeter, a half-sphere onto which spot stimuli are projected, is the premiere device for this mapping. The normal visual field extends approximately 90° temporally, 45° superiorly, 55° nasally, and 65° inferiorly. Practically, this

Oculomotor n. root of ciliary ganglion (motor) Short ciliary nn. Ciliary Oculomotor (III) n. ganglion Accessory oculomotor (Edinger-Westphal) nucleus (autonomic)

Ciliary m.

Sympathetic root of ciliary ganglion

Dilator of pupil Sphincter of pupil Optic (II) n. Nasociliary n. Long ciliary n. Nasociliary n. root of ciliary ganglion Ophthalmic a. Ophthalmic n. Trigeminal ganglion

Middle ear Internal carotid plexus Tectospinal tract Thoracic part of spinal cord

Internal carotid a. Superior cervical sympathetic trunk ganglion 1st thoracic sympathetic trunk ganglion

White ramus communicans

Gray ramus communicans Presynaptic Sympathetic fibers Postsynaptic Presynaptic Parasympathetic fibers Postsynaptic Afferent fibers Visual pathway Descending pathway Figure 1-4  Autonomic Innervation of Eye.

T1

T2

T3



CHAPTER 1  •  Clinical Neurologic Evaluation  9

Table 1-1  Pupillary Abnormalities Argyll Robertson

Horner

Holmes Adie

Yes Normal

Margins Associated changes Causes

None Brisk reaction to near stimulus Converge Irregular Iris depigmentation Tabes dorsalis

None Tonic reaction to near stimulus Accommodation Regular Loss of MSR Ciliary ganglion

Anatomy

Unknown (tectum of midbrain likely)

Response to light Other responses

Regular Ptosis Carotid dissection Carotid aneurysm Pancoast tumor Syringomyelia Loss of sympathetic

Loss of parasympathetic

MSR, Muscle stretch reflex.

contralateral constriction of the unstimulated pupil as well. These responses are called the direct and consensual reactions, respectively, and are mediated through parasympathetic innervation to the pupillary sphincter from the Edinger-Westphal nucleus along the oculomotor nerve. The pupils also constrict when shifting focus from a far to a near object (accommodation) and during convergence of the eyes, as when patients are asked to look at their nose. The sympathetic innervation of the pupillary dilator muscle involves a multisynaptic pathway with fibers ultimately reaching intracranially along the course of the internal carotid artery. Branches innervate the eye after traveling through the long and short ciliary nerves. The ciliospinal reflex is potentially useful when evaluating comatose patients. In this setting, if the examiner pinches the patient’s neck, the ipsilateral pupil should transiently dilate. This provides a means to test the integrity of ipsilateral neuropathways to midbrain structures. The short ciliary nerve, supplying parasympathetic inputs to the pupil, may be damaged by various forms of trauma. This results in a unilateral dilated pupil with preservation of other third nerve function. Significant unilateral pupillary abnormalities are usually related to innervation changes in pupillary muscles. A number of pathophysiologic mechanisms lead to mydriasis (pupillary dilatation) (Table 1-1). Atropine-like eye drops, often used for their ability to produce pupillary dilation, inadvertent ocular application of certain nebulized bronchodilators, and placement of a scopolamine anti-motion patch with inadvertent leak into the conjunctiva are occasionally overlooked as potential causes for an otherwise asymptomatic, dilated, poorly reactive pupil. Other medications may also lead to certain atypical light reactions. The presence of bilateral dilated pupils, in an otherwise neurologically intact patient, is unlikely to reflect significant neuropathology. In contrast, the presence of prominent pupillary constriction most likely reflects the use of narcotic analogs or parasympathomimetic drugs, such as those typically used to treat glaucoma. HORNER SYNDROME

The classic findings include miosis (pupillary constriction), subtle ptosis, and an ipsilateral loss of facial sweating. Here the constricted pupil develops secondary to interference with the

Interruption of the sympathetic fibers outside the brain causes ipsilateral ptosis, anhidrosis, and miosis without abnormal ocular mobility. Figure 1-5  Right Horner Syndrome.

sympathetic nerves at one of many different levels along its long intramedullary (brain and spinal cord) and complicated extracranial course. Sympathetic efferent fibers originate within the hypothalamus and traverse the brainstem and cervical spinal cord, then exit the upper thoracic levels and course rostrally to reach the superior cervical ganglia (see Fig. 1-4). Subsequently, these sympathetic fibers track with the carotid artery within the neck to reenter the cranium and subsequently reach their destination innervating the eye’s pupillodilator musculature. Typically, patients with Horner syndrome have an ipsilateral loss of sweating in the face (anhidrosis), a constricted pupil (miosis), and an upper lid droop from loss of innervation to Muller’s muscle, a small smooth muscle lid elevator (ptosis). The levator palpebra superioris, a striated muscle innervated by the oculomotor nerve CN-III, is not affected (Fig. 1-5). OPTIC FUNDUS

The ability to peer into the patient’s eye is a very unique and fascinating experience as it provides an opportunity to directly examine not only the initial portion of the optic nerve but also tiny arterioles and veins. This is the only portion of human anatomy that provides the physician with such an option. Here one may find signs of increased intracranial pressure or evidences of the effects of poorly controlled hypertension or diabetes mellitus. Today all of these various lesions are much less commonly observed because of much better treatment of systemic illnesses that affect the smaller blood vessels. Similarly the

10  SECTION I  •  Initial Clinical Evaluation

Optic fundus with papilledema

Visual field changes with enlarged blind spots secondary to chronic papilledema Figure 1-6  Effects of Increased Intracranial Pressure on Optic Disk and Visual Fields.

development of MRI and CT scanning makes it easier to identify intracerebral mass lesions at a much earlier stage of illness. Today as brain tumors no longer reach a critical size, obstructing cerebrospinal fluid flow, creating the increased intracranial pressure that leads to papilledema, this is now a relatively rare finding but one that still demands recognition. A careful optic funduscopic examination is essential in the evaluation of very many neurologic disorders. This evaluation is best performed in a relatively dark environment that leads to both a reflex increase in pupillary size and improvement in contrast of the posterior chamber structures. Findings that should be documented include optic nerve margins, venous pulsations, and the presence of hemorrhages, exudates, or any obvious obstruction to flow by embolic material (such as cholesterol plaque in patients complaining of transient visual obscuration), and pallor of retinal fields that may reflect ischemia. Papilledema is characterized by elevation and blurring of the optic disk, absence of venous pulsations, and hemorrhages adjacent to and on the disk (Fig. 1-6). The finding of papilledema indicates increased intracranial pressure of any cause, including brain tumors, subarachnoid hemorrhage, metabolic processes, pseudotumor cerebri, and venous sinus thrombosis.

III, IV, VI: Oculomotor, Trochlear, and Abducens Nerves Our ability to acutely focus our eyes on an object of interest depends on being able to move the eyes together in a conjugate fashion; this requires three related cranial nerves that take their origin from various juxta midline midbrain and pontine nuclei. These provide us with the ability to astutely focus on an object of interest without concomitantly moving our head. Whether it

is a detective watching a suspect or a teenager taking a furtive glance at a new classmate, these cranial nerves provide us with a broad sweep of very finely tuned motor function. There is no other group of muscles that are so finely innervated as these. Their innervation ratio is approximately 20 : 1 in contrast to those of large muscles of the extremities with ratios between 400 and 2000 to 1. Certainly, this accounts for the fact that one of the earliest clinical manifestations of myasthenia gravis relates to the extraocular muscles (EOMs), where the interruption of just a few neuromuscular junctions affects the finely harmonized EOM function, leading to a skewed operation and thus double vision. In order to identify isolated EOM dysfunction, it is most accurate to test each eye individually describing the observed specific loss of EOM function. For example, when the eye cannot be turned laterally, the condition is labeled as an abduction paresis, as opposed to CN-VI palsy. This is because the responsible lesion can be at any one of three sites, namely, cranial nerve, neuromuscular junction, or muscle per se. A more detailed assessment of these cranial nerves is available in Section II, Chapter 5. The medial longitudinal fasciculus (MLF) is responsible for controlling EOM function because it provides a means to modify central horizontal conjugate gaze circuits. The medial longitudinal fasciculus connects CN-III on one side and CN-VI on the opposite side. Understanding the circuit of horizontal conjugate gaze helps clinicians appreciate the relation between the frontal eye fields and the influence it exerts on horizontal conjugate gaze (see Fig. 1-6) as well the reflex relation between the ocular and vestibular systems (Fig. 1-7). The connection of the vestibular system to the medial longitudinal fasciculus can be tested by two different means. One is the doll’s-eye maneuver. Here the patient’s head is rotated side to side while the examiner watches for rotation of the eyes. Passive movement of the head to the left normally moves the eyes in the opposite direction, with the left eye adducting and the right eye abducting. The opposite occurs when the head is rotated to the right. Ice-water caloric stimulation provides another option to study vestibular ocular MLF pathways. This is primarily used for the examination of comatose patients; on very rare occasions, it is extremely helpful for rousing a patient presenting with a suspected nonorganic, that is, feigned coma. Patients are placed at an elevation of approximately 45°. Next, the tympanic membranes are checked for intactness, and then 25–50 mL of ice water is gradually infused into each ear. A normal response in the awake patient, after left ear stimulation, is to observe slow deviation of the eyes to the left followed by rapid movement (nystagmus) to the right (see Fig. 1-10). In contrast, the comatose patient with an intact brainstem has a persistent ipsilateral deviation of the eyes to the site of stimulation with loss of the rapid eye movement component to the opposite side. The center for vertical conjugate gaze and convergence is also located within the midbrain, although the underlying circuit is not well delineated. The vertical conjugate gaze centers can be tested by flexion of the neck while holding the eyelids open and watching the eye movements. When CNS processes affect conjugate gaze, such as with MS, a prominent nystagmus is often defined. The nystagmus is thought to result from an



CHAPTER 1  •  Clinical Neurologic Evaluation  11

Excitatory endings Inhibitory endings Indeterminate endings

Frontal eye fields (Brodmann area 8)

Occipital eye fields (Brodmann areas 17, 18, 19)

Interstitial nucleus of Cajal

Superior colliculus Superior oblique m.

Oculomotor nucleus

Superior rectus m. Medial rectus m. Oculomotor (III) n. Abducens internuclear neuron Trochlear nucleus

Trochlear (VI) n. Corticoreticular fibers

Lateral rectus m.

Inferior rectus m.

Medial longitudinal fasciculi Abducens nucleus

Inferior oblique m.

Ascending tract of Deiters

Superior Medial Lateral Inferior

Vestibular nuclei

Vestibular n. Abducens (VI) n. Pontine reticular formation Figure 1-7  Control of Eye Movements.

attempt to maintain conjugate function of the eyes and minimize double images.

V: Trigeminal Nerve Our ability to perceive various stimuli applied to the face depends almost entirely on this nerve; whether as a warning to protect oneself from subzero cold, something potentially threatening to our eyesight, or the pleasurable sensation from the kiss of a beloved one, all forms of sensations applied to the face are tracked to our brain through the trigeminal nerve (Fig. 1-8). The primary sensory portion of this nerve has three divisions, ophthalmic, maxillary, and mandibular; they respectively supply approximately one third of the face from top to bottom, as well as the anterior aspects of the scalp. The angle of the jaw is spared within the trigeminal mandibular division territory. This provides an important landmark to differentiate patients with conversion disorders or obvious secondary gain as they are not

anatomically sophisticated and will report they have lost sensation in this. The clinical testing of trigeminal nerve function includes both appreciation of a wisp of cotton and a sharp object on the facial skin per se as well as the corneal reflex. To evaluate the broad spectrum of facial sensation, that is, touch, pain, and temperature, the examiner uses a cotton wisp; the tip of a new, previously unused safety pin; and the cold handle of a tuning fork. In a symmetric fashion, the physician asks whether the patient can perceive each stimulus in the three major divisions of the trigeminal nerve supplying the face. The corneal reflex depends on afferents from the first division of the trigeminal nerve combined with facial nerve efferents. This is also best tested using a wisp of cotton approaching the patient from the side while she or he looks away. Normally, both eyelids close when the cornea on one side is stimulated; this is because this reflex involves multisynaptic brainstem pathways.

12  SECTION I  •  Initial Clinical Evaluation

Sensory distribution of trigeminal (V) nerve Trigeminal (semilunar) ganglion Ophthalmic n. Frontal n. Nasociliary n. Lacrimal n. Supraorbital nn. Ant. and post. ethmoidal nn. Int. nasal nn. Ext. nasal n. Maxillary n. Zygomatico-temporal n. Zygomaticofacial n. Infraorbital n.

Mandibular n. Auriculotemporal n. Buccal n. Lingual n. Inf. alveolar n. Inf. dental and gingival branches

Sup. alveolar nn. Sup. dental and gingival branches Post. nasal nn. Palatine nn. Pharyngeal branch Mental n.

Ophthalmic n.

Zones of skin innervation of trigeminal nerve divisions

Maxillary n.

Mandibular n. Cervical plexus branches

Figure 1-8  Trigeminal Nerve Neuralgia.

Lastly, there is a primary motor portion that is part of the trigeminal nerve. It primarily supplies the muscles of mastication. It is best assessed by having the patient bite down and try to open the mouth against resistance.

VII:  Facial Nerve Facial expression is one of our very important innate human attributes allowing one to demonstrate a very broad spectrum of human emotions, especially happiness and sorrow; these are primarily dependent on the facial nerve (Fig. 1-9). The motor functions of CN-VII are tested by asking patients to wrinkle their forehead, close their eyes, and smile. Whistling and puffing up the cheeks are other techniques to test for subtle weakness. When unilateral peripheral weakness affects the facial nerve after it leaves the brainstem, the face may look “ironed out,” and when the patient smiles, the contralateral healthy facial muscle

pulls up the opposite half of the mouth while the affected side remains motionless. Patients often cannot keep water in their mouths, and saliva may constantly drip from the paralyzed side. With peripheral CN-VII palsies, patients are also unable to close their ipsilateral eye or wrinkle their foreheads on the affected side. However, although the lid cannot close, the eyeball rolls up into the head, removing the pupil from observation. This is known as the Bell phenomena. In addition, there is another motor branch of the facial nerve; this innervates the stapedius muscle. It helps to modulate the vibration of the tympanic membrane and dampens sounds. When this part of the facial nerve is affected, the patient notes hyperacusis. This is an increased, often unpleasant perception of sound when listening to a phone with the ipsilateral ear. Lastly, the facial nerve has a few other functions. These include prominent autonomic function, sending parasympathetic fibers to both the lacrimal and the salivary glands. It also



CHAPTER 1  •  Clinical Neurologic Evaluation  13

Geniculate ganglion

Internal carotid plexus (on internal carotid artery) Otic ganglion Pterygopalatine ganglion

Facial nerve (VII) Internal acoustic meatus

Facial muscles Intermediate nerve Frontal belly (frontalis) of occipitofrontalis Motor nucleus of facial nerve

Temporal branc

Orbicularis oculi

Solitary tract nucleus

he s

Occipital belly (occipitalis) of occipitofrontalis muscle

Nasalis

Superior salivatory nucleus

Zygomati

Nerve to stapedius muscle

c

ranch

Stylomastoid foramen Posterior auricular nerve

cal b

Orbicularis oris

Buccal branches

Platysma Efferent fibers Afferent fibers Parasympathetic fibers Sympathetic fibers

Cervi

Buccinator

Glossopharyngeal nerve (IX) Chorda tympani nerve Stylohyoid muscle Submandibular ganglion

Submandibular gland Sublingual gland

Figure 1-9  Facial Nerve With Its Muscle Innervation.

subserves the important function of taste, another function providing both safety from rancid food and pleasure from a delightful wine. There is also a tiny degree of routine skin sensation represented for portions of the ear.

VIII: Cochlear and Vestibular Nerves (Auditory [Cochlear] Nerve) Many mornings some of us are blessed by a virtual ornithological symphony in our backyards. This always makes one pause and give thanks once again for this marvelous primary sensation. Here yet another cranial nerve, the cochlear, provides for the emotional highs that auditory sensations bring to the human brain. Whether it is the first cry of a newborn, the reassuring words of a loved one, or Beethoven’s seventh symphony, this unique sensation of higher animal life is tracked through this one cranial nerve. Beyond the simple test of being able to hear at all, more sophisticated clinical evaluation of CN-VIII is often challenging for the neurologist. Fortunately our otolaryngologic colleagues are able to precisely measure the appreciation of specific auditory frequencies in a very sophisticated manner. Barring the availability of these formal audiometric evaluations, simple office-based hearing tests sometimes help us demonstrate diagnostically useful asymmetries. Using a standard tuning fork, it is possible to differentiate between nerve (perceptive) deafness caused by cochlear nerve damage and that caused by middle

ear (conduction) deafness with two different applications of the standard tuning fork. We are able to test both air and bone conduction. Initially a vibrating tuning fork is placed on the vertex of the skull, Weber test, allowing bone conduction to be assessed. Here the patient is asked to decide whether one ear perceives the sound created by the vibration better than the other (Fig. 1-11). If the patient has nerve deafness, the vibrations are still appreciated more in the normal ear. In contrast, with conduction deafness, the vibrations are better appreciated in the abnormal ear. The Rinne test is carried out by placing this vibrating instrument on the mastoid process of the skull. Here the patient is asked to identify the presence of sound. As the vibrations of the tuning fork diminish, eventually the patient is unable to appreciate the sound. At that instant, the instrument is moved close to the external ear canal to evaluate air conduction. If the individual has normal hearing, air conduction is longer than bone conduction. When a patient has nerve (perceptive) deafness, both bone and air conductions are diminished, but air conduction is still better than bone conduction. In contrast with conduction deafness, secondary to middle ear pathology, these findings are reversed. Here, when the patient’s bony conduction has ceased, air conduction is limited by the intrinsic disorder within the middle ear. Therefore, the sound can no longer be heard; that is, it cannot pass through the mechanoreceptors that amplify the sound and thus cannot reach the auditory nerve per se.

14  SECTION I  •  Initial Clinical Evaluation

Slow phase

Rapid phase (saccadic movement)

Direction of maintained head acceleration

Direction of maintained head acceleration Horizontal semicircular canal depressed

Horizontal semicircular canal excited

Medial rectus motor neurons excited Ascending tract of Deiters

Medial rectus motor neurons depressed Abducens internuclear neuron Inhibitory interneurons

Medial and lateral vestibular nuclei, excited Abducens nucleus depressed Oculomotor (III) nerve Lateral rectus muscle

Abducens nucleus excited

Parapontine reticular formation (PPRF) Medial rectus muscles

Abducens (VI) nerve

Lateral rectus muscle

Eyes move in opposite direction to head; tend to preserve visual fixation: rate determined by degree of horizontal canal excitation

Horizontal semicircular canal depressed

Horizontal semicircular canal input continues, but is opposed by inhibition from saccadic center

Medial rectus motor neurons excited

Medial rectus motor neurons depressed

Abducens nucleus depressed Inhibitory burst interneuron

Vestibular nuclei depressed by saccadic center Abducens nucleus excited by saccadic center

Excitatory burst interneuron Saccadic center (parapontine reticular formation [PPRF])

Abducens (VI) nerve

Medial rectus muscles

Lateral rectus muscle

Oculomotor (III) nerve Lateral rectus muscle

Eyes snap back in same direction as head

Figure 1-10  Vestibular Eighth Nerve Input to Horizontal Eye Movements and Nystagmus.

VESTIBULAR NERVE

The vestibular system can be tested indirectly by evaluating for nystagmus during testing of ocular movements or by positional techniques, such as the Barany maneuver, that induce nystagmus in cases of benign positional vertigo (BPV) where inner ear dysfunction is caused by otolith displacement into the semi­ circular canals (Fig. 1-12). Here the patient is seated on an examining table and the eyes are observed for the presence of spontaneous nystagmus. If none is present, the examiner rapidly lays the patient back down, with the head slightly extended and concomitantly turning the head laterally. If after a few seconds’ delay, the patient develops the typical symptoms of vertigo with a characteristic delayed rotary, eventually fatiguing nystagmus, the study is positive. Eye movements depend on two primary components, the induced voluntary frontal eye fields and the primary reflexdriven vestibular–ocular movement controlled by multiple connections (Fig. 1-10; see also Fig. 1-7). The ability to maintain conjugate eye movements and a visual perspective on the surrounding world is an important brainstem function. It requires inputs from receptors in muscles, joints, and the cupulae of the inner ear. Therefore, when the patient has dysfunction involving any portion of the vestibular-ocular or cerebellar axis, the maintenance of basic visual orientation is challenged. Nystagmus is a compensatory process that attempts to help maintain visual fixation.

Traditionally, when one describes nystagmus, the fast phase direction becomes the designated title (see Fig. 1-10). For example, left semicircular canal stimulation produces a slow nystagmus to the left, with a fast component to the right. As a result, the nystagmus is referred to as right beating nystagmus. Direct stimulation of the semicircular canals or its direct connections, that is, the vestibular nuclei, often induces a torsional nystagmus. This is described as clockwise or counterclockwise, according to the fast phase. A few beats of horizontal nystagmus occurring with extreme horizontal gaze is normal in most individuals. The most common cause of bilateral horizontal nystagmus occurs secondary to toxic levels of alcohol ingestion or some medications, that is, phenytoin and barbiturates.

IX, X, XI: Glossopharyngeal, Vagus, and Accessory Nerves The most common complaints related to glossopharyngealvagal system dysfunction include swallowing difficulties (dysphagia) and changes in voice (dysphonia). A patient with a glossopharyngeal nerve paresis presents with flattening of the palate on the affected side. When the patient is asked to produce a sound, the uvula is drawn to the unaffected side (Fig. 1-13). Indirect mirror examination of the vocal cords may demonstrate paralysis of the ipsilateral cord. The traditional test for gag



CHAPTER 1  •  Clinical Neurologic Evaluation  15

Weber Test

Tone referred to poorer ear Poorer ear indicates conductive impairment.

Stage 1

With patient seated on table and head turned to right, quickly lower him to supine position with head over edge 30˚ below horizontal. Observe eyes for appearance of nystagmus.

Better ear

Tone referred to better ear indicates perceptive impairment.

Rinne Test Stage 2

Repeat test with head turned to left.

Normal: air conduction is twice as long as bone conduction. Conductive loss: Bone conduction longer or equal to air conduction. Receptive or SNHL: Air conduction longer than bone conductions but both variably shortened.

Figure 1-11  Auditory Nerve Testing: Weber and Rinne Testing.

reflex, placing a tongue depressor on the posterior pharynx, is of equivocal significance at best, because the gag response varies significantly and patients evidence wide varieties of tolerance to this stimulus. Preservation of swallowing reflexes is best tested by giving the patient 30 mL of fluid to drink through a straw while seated at 90°. Patients with compromised swallowing reflexes develop a “wet cough” and regurgitate fluids through their nose. Intracranial or proximal spinal accessory nerve damage limits the ability to turn the head to the opposite side (weakness of the ipsilateral sternocleidomastoid muscles and trapezius muscle). More distal accessory nerve damage is most commonly seen following surgical misadventures during biopsying a lymph node from the posterior triangle of the neck, sparing the sternocleidomastoid but affecting the trapezius, causing dysfunction and winging of the scapula.

XII: Hypoglossal Nerve Damage to the hypoglossal nucleus or its nerve produces tongue atrophy and fasciculations The fasciculations usually are seen best on the lateral aspects of the tongue. If the nerve damage is unilateral, the tongue often deviates to that side (see Fig. 1-13). Two means to test for subtle weakness include asking the patient to push against a tongue depressor held by the examiner and having the patient push the tongue into the cheek.

Repeat test with patient facing straight ahead. Figure 1-12  Test for Positional Vertigo.

CRANIAL NEUROPATHIES AND SYSTEMIC DISEASE When one evaluates a patient presenting with any cranial neuropathy, it is important to search for signs of other neurologic and systemic disorders. The patient with recently dis­ covered anosmia may have early Parkinson disease. An acute painful, but pupil sparing, third nerve palsy may be a tip-off to the diagnosis of diabetes mellitus. When one meets an individual with unilateral or bilateral Bell palsies, Lyme disease, as well as sarcoidosis, always requires consideration in the differential diagnosis. When one evaluates patients having multiple cranial neuropathies, leptomeningeal infiltration from metastatic carcinoma or lymphoma, sarcoidosis or chronic infectious processes, such as tuberculosis, always require diagnostic consideration.

CEREBELLAR DYSFUNCTION Evaluation of posture and gait provides the opportunity to observe the most dramatic clinical manifestations of cerebellar dysfunction. The patient presenting with midline cerebellar lesions affecting the vermis characteristically assumes a broad-based stance when walking that typically mimics an inebriated individual. At the extreme, these individuals are unable to maintain a stance. In contrast, when there is a cerebellar hemisphere problem, the patient has a tendency to veer to the affected side. With

16  SECTION I  •  Initial Clinical Evaluation

Left glossopharyngeal paralysis: uvula drawn to nonparalyzed right side when patient says “A-AH”

Right hypoglossal nerve paralysis: tongue deviates toward paralyzed side when protruded

Left vocal cord paralysis Left vagus nerve paralysis: accumulation of saliva in piriform fossa on affected side due to cricopharyngeal muscle paralysis and inability to swallow Figure 1-13  Uvula, Tongue, and Vocal Cord Weakness.

midline lesions, gait is usually unchanged whether the eyes are open or closed, suggesting that this is not the result of disruption of proprioceptive inputs. Patients with unilateral lesions are often able to compensate with their eyes open but deteriorate when they lose visual inputs. Loss of limb coordination is the result of cerebellar inability to calculate inputs from different joints and muscles and coordinate them into smooth movements. This abnormality is best observed by testing finger-to-nose and heel-to-shin movements and making bilateral comparisons. When performing the fingerto-nose test, the examiner provides his or her finger as the target; it is sequentially moved to different locations. The patient in turn keeps the arm extended and tries to touch the examiner’s finger at each location. When unilateral cerebellar dysfunction is present, the patient overshoots the target, so-called past pointing. It is important not to misinterpret such findings as always of cerebellar origin, as patients with focal motor or sensory cerebral cortex lesions may present with mild arm weakness and proprioceptive sensory loss affecting that limb. In this setting, a degree of focal limb dysmetria may develop; this is sometimes difficult to distinguish from primary cerebellar dysfunction. One clinical means to distinguish cerebellar from cerebral cortical dysfunction is that the patient with cerebellar hemisphere lesions will have these movements improve after a few trials. In contrast, with cerebral cortical

dysmetria, repeated trials only lead to further deterioration in the attempted action. Dysdiadochokinesia is a sign of cerebellar dysfunction that occurs when the patient is asked to rapidly change hand or finger movements, that is, alternating between palms up and palm down. Patients with cerebellar dysfunction typically have difficulties switching and maintaining smooth, rapid, alternating movements. Tremor, nystagmus, and hypotonia are other important indications of potential cerebellar dysfunction. Tremors may develop from any lesion that affects the cerebellar efferent fibers via the superior cerebellar peduncle. This is characterized by coarse, irregular movement. Nystagmus may occur with unilateral cerebellar disease; the nystagmus is most prominent on looking to the affected side. Hypotonia may be present but is often difficult to document. This is best observed when testing a patient’s muscle stretch reflexes at the quadriceps tendon knee jerk. Here, the normal “check” does not occur after the initial movement, so the leg on the affected side swings back and forth a few times after the initial patellar tendon percussion.

GAIT EVALUATION Whenever possible, the neurologic clinician is encouraged to personally greet the patient, watching them arise from their



CHAPTER 1  •  Clinical Neurologic Evaluation  17

A Parkinson Disease 1

2

Stage 1: unilateral involvement; blank facies; affected arm with tremor

3

Stage 2: bilateral involvement with stooped posture; slow, shuffling gait with short steps (petit pas)

C Cerebellar Gait 1

B Spastic Corticospinal 1

Stage 3: pronounced gait disturbances, moderate generalized disability; postural instability with tendency to fall

Typical wide-based gait of drug intoxication

Wide-based gait of midline cerebellar tumor or other lesion

Apraxic gait of normalpressure hydrocephalus

Patient walks gingerly due to loss of position sense and/or painful dysesthesia

2

Sudden buckling of knee while going down stairs (femoral nerve)

Typical spastic gait, circumduction of the leg at the hip and scuffling the toe on affected leg.

E Lumbar Spine Disease 1

F Peripheral Neuropathies 1

Right hemiparesis with flexed right arm secondary to a corticospinal tract lesion

D Apraxic, Frontal Gait

2

2

Characteristic posture in left-sided lower lumbar disc herniation

2

Patient with lumbar spinal stenosis with forward flexion gait

G Myopathy

3

Sudden occurrence of foot drop while walking (peroneal nerve)

Severe myopathy or NMJ lesion with proximal weakness

Figure 1-14  Gait Disorder Characteristics and Etiology.

chair and initiate their gate. Next, before moving to the examination room the patient needs to be observed walking in the hallway. On occasion it is important to observe the patient on stairs particularly if there is a query about proximal weakness. A smooth gait requires multiple inputs from the cerebellum and primary motor and sensory systems. Gait disorders provide a very broad differential diagnostic challenge that results from lesions in any part of the neuraxis (Fig. 1-14). Frontal lobe (Fig. 1-14,D) processes including tumors and normal-pressure hydrocephalus lead to apraxia, spasticity, and

leg weakness. Spasticity per se is a nonspecific marker of corticospinal tract disorders that may arise with various neurologic lesions between the frontal lobe and the distal spinal cord (Fig. 1-15). Various neurodegenerative conditions, particularly those affecting the basal ganglia, such as Parkinson disease (Fig. 1-15,A1–3), are some of the most common causes of gait difficulties. These are typically manifested by slowness initiating gait, small steps, and eventually gait festination, wherein once patients begin to accelerate their walking, they take increasingly more rapid but paradoxically smaller steps. There is an innate,

Hip

Knee

Primary motor cortex (area 4)

Ankle Toes

Trunk Should er Elbow

18  SECTION I  •  Initial Clinical Evaluation

Hip Trunk Arm

t ris W gers Fin b Thum Neck

Hand

Face

Brow Eyelid Nares Lips Tongue Larynx

Posterior limb

Lateral aspect of cerebral cortex to show topographic projection of motor centers on precentral gyrus

Internal capsule Posterior

Visual and auditory

Anterior limb

Temporopontine

L Tr eg u Ar nk m Face

Midbrain III, IV

Sensory Corticospinal (pyramidal) Frontopontine

Anterior Pons

V

Horizontal section through internal capsule to show location of principal pathways

VII

IX X XI XII

Frontothalamic

Decussation of pyramids

Decussation

Lateral (crossed) corticospinal tract

Spinal cord

Anterior (direct) corticospinal tract

Ventral aspect of brainstem showing decussation of pyramids

Figure 1-15  Pyramidal System, Corticospinal Tract. Gait Disorders Can Arise From Interruption of These Pathways at Any Level.

almost wax-like rigidity to their stooped body carriage, including the frozen posture of one or both arms that usually lack the normal arm swing. Very occasionally, a change in posture from the seated position to attempted gait will be manifested by a dystonic posturing, which may be indicative of another genetic disorder, dystonia musculorum deformans or paroxysmal choreoathetosis. Cerebellar disorders related to midline anterior cerebellar vermis lesions or various heredofamilial spinocerebellar entities lead to a broad-base gait ataxia (Fig. 1-14,C1–2). The patient is asked to walk in tandem, with one foot in front of the other. It is an effective means to elicit a subtle disequilibrium often related to midline cerebellar dysfunction such as with simple entities, including alcohol intoxication. Myelopathies with posterior column dysfunction, such as vitamin B12 deficiency, present with loss of proprioception

function. These particularly affect the patient’s gait in dark environments, as do some of the peripheral neuropathies, especially those with a primary sensory ganglionopathy (Fig. 1-14,F1). Testing for the presence of a Romberg sign is an excellent clinical marker for these disorders. Here patients are asked to stand in place with their eyes open, gain their equilibrium, and then close their eyes. Individuals with various proprioceptive disorders are unable to maintain their balance when visual clues are withdrawn; such a condition is referred to as a positive Romberg sign. One of the earliest signs, and at times a prominent sign of a myopathy, is needing to push off the arms of a chair when arising to walk. When these individuals do walk their gait may be a broad-based gait mimicking an anterior cerebellar lesion. When viewed from the side the curve of their low back is accentuated, i.e. hyperlordotic. Both the wide base and the hyperlordosis are representative of weakness of the most



proximal muscle groups—the iliopsoas, quadriceps, and glutei— as well as the paraspinal axial musculature. An often overlooked cause of gait difficulties is ortho­ pedic and musculoskeletal problems. A perhaps simplistic perspective on the contribution of this system to gait is the analogy that the musculoskeletal system functions similar to an axle on a car, maintaining alignment and proper, symmetric rotation of the wheels. Our vertebral column is a sophisticated axle that with time loses some of its alignment. The attached muscles, to a misaligned chain of vertebrae, ultimately generates aberrant feedback loops to the spinal cord and the brain. Many of our senior citizens gradually lose precise control of their gait, initially manifested by subtle changes on neurologic exam. Healthy older individuals often have limited ability to perform tandem gait. The very important message here is that this finding in isolation should not be considered abnormal per se among patients living into their eighth decade. Nevertheless, older patients become increasingly limited by a dwindling ability to walk independently. Very often, in this setting there is not one specific mechanism either operative or identifiable. A number of patients have a multifaceted source related to the gradual aging (graying) of multiple neurologic systems. One source that always requires consideration is the possibility of orthostatic hypotension. Most commonly, this relates to medications; however, one of the neurodegenerative disorders, multiple system atrophy (see Chapter 34), may present in this fashion. Thus, it is important to carefully check blood pressures in the supine posture, when seated, then immediately on standing, and then every 30 seconds thereafter until the pressure is stabilized. A persistent drop in blood pressure of 20–30/15 mm Hg is usually regarded as significant in this setting. It is important to ask about the circumstances accompanying the gait decline. Does the individual scuff a foot because of a spastic leg that interferes with a smooth alteration of individual legs? What settings lead to a fall? Does one catch one’s toe on a rug as with subtle spasticity (Fig. 1-14,B1–2) or feel a leg give out going downstairs secondary to weakness of the quadriceps femoris muscle (Fig. 1-14,F2)? Having such information, the examiner can then easily try to reproduce the circumstances that lead to the falls. Typically, gait function is tested under several conditions, including walking straight, walking at least 10 yards in open space, making turns, maneuvering through a tight corridor, attempting tandem gait, or in low light settings as well as on the stairs. The normal degree of foot separation (the base) is widened when proprioception or midline cerebellar vermis function is compromised. Occasionally, having the patient climb stairs reveals a subtle degree of iliopsoas weakness as found in various peripheral motor unit disorders (particularly myopathies) and, less commonly, neuromuscular junction or proximal peripheral neuropathies (Fig. 1-14,G). Finally, the appearance of spasticity may be enhanced by having the patient walk longer distances and even asking him or her to walk several blocks and return to the clinic. Rarely, this uncovers an unsuspected corticospinal tract lesion. Chapter 32 expands on the clinical evaluation of gait disorders.

CHAPTER 1  •  Clinical Neurologic Evaluation  19

ABNORMAL ADVENTITIOUS MOVEMENTS Neurologists are frequently consulted to evaluate various adventitious movements, including tremors, chorea, dyskinesias, and ballismus. The most common movement disorder encountered in the office is “essential tremor,” usually a “benign” hereditary condition that generally does not herald a progressive neurodegenerative process. These patients often seek medical attention because they are concerned that their tremors are a sign of Parkinson disease. Therefore, differentiating between different types of tremors is a common and important concern. An essential tremor characteristically occurs during certain voluntary actions, such as when bringing a cup of coffee to the mouth. In contrast, with classic Parkinson disease, the pill-rolling tremor is primarily evident at rest and when the patient is seated or walking and disappears with the spontaneous use of the extremity. A subtle fidgeting may represent the earliest sign of Huntington or Sydenham chorea. Very rarely a patient will present with a more energetic, purposeless, wing beating movement of an extremity referred to as hemiballismus. A full discussion of movement disorders and their presentation is found in Section VII.

MUSCLE STRENGTH EVALUATION Weakness is one of the most common complaints of patients seeking neurologic care. The motor pathways encompass multiple anatomic areas within the CNS, including the cerebral cortex and important subcortical structures such as the basal ganglia, the brainstem, the cerebellum, the spinal cord, and the peripheral motor unit (Fig. 1-16). Although complaints of generalized weakness, fatigue, or both often are not caused by a specific neurologic condition, the possibility of multiple sclerosis in younger individuals and Parkinson disease in older patients always needs to be considered. When the patient is significantly overweight or has a neuromuscular disorder, sleep apnea needs consideration as a cause of fatigue or a feeling of “weakness.” Peripheral motor unit disorders are important considerations for the differential diagnosis of a patient with generalized weakness. These include processes affecting the anterior horn cell (i.e., amyotrophic lateral sclerosis), peripheral nerve (i.e., Guillain–Barré syndrome or chronic inflammatory demyelinating disorders), neuromuscular junction (including Lambert–Eaton myasthenic syndrome [LEMS]), or muscle cells (various myopathies). Partial limb weakness is referred to as monoparesis. Total limb paralysis is referred to as monoplegia. Unilateral weakness of the limbs is referred to as hemiparesis or hemiplegia. Paraparesis refers to involvement of both legs; if no motor function remains, this is considered paraplegia. Similarly, quadriplegia relates to total paralysis of all 4 extremities. Focal weakness often has a subtle character that frequently is not recognized by the patient as loss of motor strength. Dropping objects or clumsy handwriting may represent a single peripheral nerve lesion such as a radial neuropathy leading to a wrist drop. Tripping on rugs or steps may be the expression of a peroneal nerve lesion causing a foot drop (Fig. 1-14,F3). In

20  SECTION I  •  Initial Clinical Evaluation

Disorder

Anatomical site of lesion 1. Cortex

Neurologic findings

1. Stroke, tumor

Brisk muscle stretch reflexes, positive Babinski sign

2. Parkinson disease

Tremor, rigidity, cogwheeling, petit pas gait; facial masking

2. Basal ganglia 3. Cranial motor nerve/nuclei 4. Cerebellum 5. Spinal cord

3. Multiple cranial neuropathies 4. Cerebellar ataxia

Gait or extremity ataxia

5. Spinal injury, auto/diving accident; MS, abscess, tumor

Sensory loss, increased deep tendon reflexes, positive Babinski sign

6. Motor neuron disease

Increased muscle stretch reflexes, no sensory loss, variable body and tongue fasciculations

7. Neuropathies

Diminished muscle stretch reflexes, decreased nerve conduction velocity Positive edrophonium chloride test, facial weakness, pupillary abnormality

6. Anterior horn cell 7. Peripheral nerve; root, plexus; mono or generalized neuropathy 8. Motor end plate 9. Muscle

8. Myasthenia gravis, LEMS, botulism

10. Connective tissue

9. Myopathies

Muscle stretch reflexes normal or decreased, muscle enzynes increased

10. Congenital hypotonia, Marfan syndrome, Ehlers-Danlos syndrome

Muscle stretch reflexes normal or slightly decreased

Figure 1-16  Primary Sites of Motor Disorders.

contrast, dramatic whole limb weakness is obvious and of greater patient concern, often leading to immediate medical attention as occurs with a stroke. Bilateral motor loss without cognitive or visual difficulties is most commonly due to lesions affecting the spinal cord or the peripheral nervous system and muscle. When analyzing the complaint of weakness, the physician must consider the presence or absence of associated neurologic complaints or difficulties, such as language, speech, and visual changes; gait dysfunction; difficulty with rising from chairs and associated movements; and alteration in sensation. The neurologist testing for strength must search for evidence of atrophy and fasciculations, or spasticity. Equally important is the need to note the degree of patient effort and cooperation, as well as to consider associated problems that may compromise the testing, such as pain and skin or orthopedic lesions. Formal strength testing must be conducted in a systematic manner evaluating successive areas of the motor unit beginning at the brain and proceeding distally to the individual muscles per se (see Fig. 1-16). Here one places an initial focus on the major muscle groups, such as the flexors and extensors, to seek out any areas of weakness. More specific muscle testing is particularly useful when distinguishing between lesions of the nerve root, plexus, or mononeuropathies (Table 1-2). When individual muscle testing does not demonstrate specific weakness, other techniques sometimes uncover more lessobvious functional loss. If the patient is instructed to extend the

arms with the palms up and the eyes closed, subtle arm weakness may manifest as a pronating downward or lateral drift of the affected extremity. Similarly, moving the fingers as if playing piano or rapidly tapping may demonstrate a subtle in-coordination. Subtle proximal lower extremity weakness may not be appreciated with individual muscle testing. Watching the patient rise from a chair may demonstrate use of furniture arms to “push off” and is a good means to identify early proximal leg weakness. One particularly effective means to uncover proximal leg weakness is to observe the patient climb stairs or squat and attempt to rise without using their arms. Also asking the patient to walk on the heels or the tips of the toes is helpful in uncovering distal leg weakness.

Grading Weakness The traditional, most widely used British system for quantifying degrees of weakness is based on a scoring range of 0 to 5, with 5 being normal. The extremes of grading are easy to understand, although the subtle grading between 4 and 5 (i.e., >4, 4, >4, or 25 years • Chronic and severe tic disorder with severe functional impairment • Failure of conventional medical therapy for tics • Trial of behavioral treatment, if suitable •  Optimization of treatment of comorbid medical, neurologic and psychiatric disorders for >6 months •  Active involvement and compliance with psychological interventions to address psychosocial problems for >6 months Exclusion Criteria • Secondary tic disorder •  Severe medical, neurologic, psychiatric, or cognitive disorders •  Significant psychosocial factors that increase the risk of the procedure or complicate recovery period •  Unwillingness to be involved in ongoing treatment for psychosocial problems

accumbens, and the anterior limb of the internal capsule. Inclusion and exclusion criteria to determine suitable TS candidates for DBS have been devised and are listed in Box 39-4. Further controlled trials of DBS in TS will need to be done to confirm the efficacy of DBS in TS and the optimal surgical target. ADDITIONAL RESOURCES Ackermans L, Temel Y, Visser-Vandewalle V. Deep brain stimulation in Tourette syndrome. Neurotherapeutics 2008;5:339-344. Rampello L, Alvano A, Battaglia G, et al. Tic disorders: from pathophysiology to treatment. J Neurol 2006;253:1-15. Shprecher D, Kurlan R. The management of tics. Mov Disord 2009; 24:15-24.

Dystonia

40 

Julie Leegwater-Kim

Clinical Vignette A 22-year-old previously healthy woman developed slurred speech, difficulty walking, and hand tremors over the course of 1 month after a severe psychological trauma. She had mild neck pain and took cyclobenzaprine without benefit. She denied history of fever, head trauma, or exposure to dopamine receptor–blocking agents. There was no family history of neurologic disease. Exam revealed lower facial dystonia, including risus sardonicus and tongue dystonia, dysarthria, bradykinesia, mild cogwheel rigidity, mild rest and kinetic tremor, dystonic gait, and loss of postural reflexes. After several weeks, her symptoms plateaued. Trial of carbidopa/levodopa was ineffective. She reported slight benefit on high doses of trihexyphenidyl. Workup included blood glucose, creatinine, electrolytes, complete blood count, liver function tests, thyroidstimulating hormone, erythrocyte sedimentation rate, antinuclear antibodies test, vitamin B12, ceruloplasmin, and 24-hour urine copper, all of which were within normal limits. Slit-lamp exam was negative for Kayser–Fleischer rings. Spinocerebellar ataxia genetic testing was negative. Brain magnetic resonance imaging was unremarkable. Electroencephalography and electromyography were unremarkable. ATP1A3 genetic sequencing revealed a mutation.

D

ystonia is a hyperkinetic movement disorder characterized by involuntary, sustained muscle contractions that frequently cause twisting and repetitive movements or abnormal postures. Dystonic movements are patterned, meaning they repeatedly involve the same group of muscles. There is simultaneous contraction of agonist and antagonist muscles. In general, the duration of dystonic muscle contractions is longer than other hyperkinesias (i.e., chorea), though sometimes the movements can be rapid enough to resemble repetitive myoclonic jerking. One of the characteristic features of dystonia is that it is often temporarily diminished by tactile sensory tricks (gestes antagonistes). For example, a patient with cervical dystonia may be able to reduce dystonic movements by placing a hand on the chin or the side of the face. Patients with orobuccolingual dystonia often experience improvement by touching the lips or placing an object, such as a toothpick, in the mouth. In some patients, simply thinking about performing the sensory trick diminishes dystonia. The efficacy of sensory tricks can be exploited in the development of therapies. For example, some patients with lower cranial dystonia may benefit from wearing a mouthguard. The initial presentation of dystonia is usually focal (affecting one body part) and task-specific—the dystonia occurs with a particular action. For example, a subject with foot dystonia may initially note dystonia when walking forward, but not walking

backward or running. In the majority of patients, the dystonia remains focal without spreading to other parts of the body. If dystonia spreads, it tends to involve contiguous body parts and becomes a segmental dystonia. In more severe cases, the dystonia can become generalized. As a rule, the younger the age at onset, the more likely the dystonia is to spread. Recent data have also suggested that in the primary dystonias there is a caudal-to-rostral anatomic gradient in the site of onset as a function of age. As dystonia progresses, it emerges with other actions of the affected body part, therefore becoming less task-specific. For example, the patient with foot dystonia may experience it when walking forwards and backwards, running, or tapping the foot. Further progression can lead to “overflow dystonia,” in which movement of a distant body part elicits the dystonia. As dystonia worsens, it can occur at rest. In the most severe cases of dystonia, contractures may develop. Dystonia is frequently worsened by fatigue and stress and diminished with relaxation and sleep. Pain is generally uncommon in dystonia except for cervical dystonia, in which ~75% of patients report pain.

CLASSIFICATION OF DYSTONIA There are several recognized classification schemes for dystonia: (1) age at onset, (2) anatomic distribution, and (3) etiology.

Age at Onset Early-onset dystonia is defined as dystonia developing at or before the age of 26 years and late onset is defined as dystonia developing after age 26 years. Age at onset is an important factor determining prognosis in patients with dystonia, with earlier age at onset correlating with increased likelihood of spread of dystonia to other body parts. In general, young-onset dystonia tends to begin in a limb and become generalized whereas adultonset dystonia tends to be craniocervical and remain focal or become segmental.

Anatomic Distribution The topographic characteristics of dystonia are useful in defining the severity of the dystonia and guiding treatment. Focal dystonia affects a single body part. Virtually any part of the body can be involved in dystonia and many types of focal dystonia have specific names: blepharospasm (dystonic eye closure), spasmodic torticollis (rotational cervical dystonia), and writer’s cramp (focal hand dystonia). When dystonia involves two or more contiguous body parts/regions, it is referred to as segmental dystonia. Multifocal dystonia refers to the involvement of two or more noncontiguous body parts. Generalized dystonia represents a combination of crural dystonia (one or both legs plus trunk) and any other area of the body. In hemidystonia, as

332  SECTION VII  •  Gait and Movement Disorders

its name implies, dystonia affects one half of the body. Hemidystonia suggests a symptomatic (secondary), rather than primary, dystonia.

Etiology The growth in our understanding of the genetics of dystonia has contributed significantly to the etiologic classification of dystonia. There are essentially two broad categories: primary and secondary.

PRIMARY DYSTONIA Primary dystonias are characterized by pure dystonia (with the exception that tremor can be present) and they may be sporadic or familial. Most primary dystonias are sporadic with onset in adulthood and a focal or segmental presentation. The most common focal dystonia presenting to movement disorders clinics is cervical dystonia (Fig. 40-1). After cervical dystonia, the most common focal dystonias are blepharospasm, spasmodic dysphonia, oromandibular dystonia, and hand dystonia. A minority of primary dystonias have an identified genetic etiology (Box 40-1). Perhaps the best studied of the primary dystonias is DYT1 dystonia, or Oppenheim’s dystonia, a generalized torsion dystonia that usually begins in childhood affecting the limbs first. DYT1 dystonia is caused by a deletion in the DYT1 gene, which encodes for the torsin A protein. The disease

Young man with muscular torticollis. Head tilted to left with chin turned slightly to right because of contracture of left sternocleidomastoid muscle.

Figure 40-1  Cervical Dystonia.

is inherited in an autosomal dominant fashion and has 30–40% penetrance. Phenotype can vary widely within an affected family. The DYT1 mutation is estimated to account for 90% of limbonset dystonia cases in the Ashkenazi Jewish population and 50–70% of cases in the non-Jewish population. A number of Box 40-1  Dystonia Classification Schemes • Age at Onset • Young-onset: ≤26 • Late-onset: >26 • Anatomic Distribution • Focal—single body part • Segmental—two or more contiguous body parts • Multifocal—two or more noncontiguous body parts • Generalized—segmental crural dystonia plus one other body part • Hemidystonia—dystonia affecting one half of the body • Etiologic • Primary (Idiopathic) Familial Sporadic • Secondary Dystonia Heredodegenerative Degenerative—sporadic Dystonia-plus syndromes (inherited nondegenerative) Drug-induced Injury/trauma Structural lesions Psychogenic

Untreated torticollis in middle-aged woman. Thick, fibrotic, tendon-like bands have replaced sternocleidomastoid muscle, making head appear tethered to clavicle. Two heads of left sternocleidomastoid muscle are prominent.



CHAPTER 40  •  Dystonia  333

Table 40-1  Genetic Dystonias Dystonia

Etiologic type

Inheritance

Clinical Features

Chromosome Gene

DYT1

Primary

Autosomal dominant

Early onset (age 25 mm) extend above the sella or into the cavernous sinus on either side of the sella and are easily identified with MRI (see Fig. 52-16). A thorough endocrine evaluation includes serum levels of prolactin, follicle-stimulating hormone and luteinizing hormone, cortisol, and growth hormone and thyroid function parameters.



CHAPTER 52  •  Brain Tumors  473

Invasive (malignant) adenoma; extension into right cavernous sinus

Large acidophil adenoma; extensive destruction of pituitary substance, compression of optic chiasm, invasion of third ventricle and floor of sella

Treatment Initially many pituitary adenoma patients primarily require medical therapy. Prolactin secreting tumors are often successfully controlled with bromocriptine, a dopamine agonist that suppresses prolactin production and concomitantly decreases tumor volume. Growth hormone–secreting tumors are often controlled with octreotide, a somatostatin analog. Small, nonsecreting pituitary tumors may often be observed for endocrine dysfunction or signs of growth with combined clinical and MRI modalities. Endocrinologically active tumors that cannot be controlled with medication are a prime indication for surgical treatment as are patients harboring a macroadenoma producing mass effect. The surgery is primarily performed using a transsphenoidal approach through the nasal cavity and the sphenoid sinus, wherein the contents of the sella can be visualized and the tumor can be removed, often sparing the pituitary gland. Postoperatively, these patients require follow-up for signs of hypopituitarism. This is particularly important for those individuals presenting with Cushing disease. Subsequent to surgery, their adrenocorticotropic hormone secretion is diminished. These patients usually require postoperative and sometimes lifelong steroid replacement. Pituitary adenoma surgery is associated with concomitant sodium balance and fluid intake problems leading to hyponatremia with polydipsia and polyuria. This necessitates careful follow-up and sometimes treatment with desmopressin acetate (DDAVP) to replace the naturally occurring antidiuretic hormone (ADH). This is a synthetic analogue of the natural pituitary hormone 8-arginine vasopressin, an ADH affecting renal water conservation.

CRANIOPHARYNGIOMA Nonfunctioning

May grow large due to lack of early endocrine symptoms; optic chiasm compressed

Bitemporal hemianopsia often initial symptom

Figure 52-15  Pituitary Macroadenoma.

Craniopharyngiomas are uncommon tumors thought to arise from a remnant of the brain’s embryologic development, namely, the Rathke pouch. These histologically benign cystic lesions, often occurring in the region of the sella, hypothalamus, or third ventricle, comprise 2–3% of all intracranial tumors. There is a greater incidence in children. Typically the presenting symptoms include visual impairment, pituitary dysfunction, and hydrocephalus. The radiographic features of craniopharyngiomas distinguish them from other tumors of the suprasellar region (Fig. 52-17). Cystic changes, variable-contrast enhancement, and calcification seen on CT occur frequently. Surgery is the treatment of choice for symptomatic craniopharyngiomas. The suprasellar location limits tumor access, making incomplete resections common. Resection is also difficult because of the intense glial reaction of the surrounding brain, causing adherence to critical brain structures and nearby blood vessels. As with pituitary surgery, cranio­ pharyngioma resection may also have a difficult postoperative course, particularly with endocrine dysfunction. Although radiation therapy and possibly radiosurgery can decrease recurrence rates, craniopharyngiomas have a high rate of local recurrence.

474  SECTION XI  •  Neuro-oncology

A. Grade of sella turcica enlargement and/or erosion Enclosed adenomas Invasive adenomas I. Sella normal, III. Localized II. Sella enlarged, IV. Entire floor floor may be indented erosion of floor but floor intact diffusely eroded

A. No suprasellar extension of tumor

B. Type of suprasellar extension B. Suprasellar bulge C. Tumor reaches 3rd does not reach floor of ventricle, distorting its 3rd ventricle chiasmatic recess

A

C

B

D

Figure 52-16  Pituitary Adenoma Gradation vis-à-vis Sella Enlargement.

D. Tumor fills 3rd ventricle almost to interventricular foramen (of Monro)

Large pituitary tumor. (A) Coronal T1weighted and (B) sagittal T1-weighted post–gadolinium-enhanced images show a dumbbell-shaped tumor within a moderately enlarged sella with a larger component protruding above and posterior to the sella with elevation and distortion of the optic chiasm.

Pituitary apoplexy in a 44-year-old man presenting with severe headache, diplopia, photophobia, nausea and vomiting. (C) Coronal T1-weighted post gadoliniumenhanced fast spin echo imaging demonstrates a large intrasellar mass with peripheral enhancement (arrowheads) and upward displacement of the optic chiasm. (D) The central nonenhanced component shows a very heterogeneous signal pattern on axial T2-weighted imaging with more compression of the left cavernous sinus (arrow) and represents a hemorrhagic necrotic pituitary adenoma.



CHAPTER 52  •  Brain Tumors  475

Tumor gently teased forward from under optic chiasm after evacuation of cystic contents via frontotemporal flap

Large cystic suprasellar craniopharyngioma compressing optic chiasm and hypothalamus, filling 3rd ventricle up to interventricular foramen (of Monro), thus causing visual impairment, diabetes insipidus, and hydrocephalus

A

B

Histologic section: craniopharyngioma (H and E stain, ×125)

C

D

A–D Sagittal T1-weighted images without A and after B gadolinium enhancement and C coronal T1-weighted gadolinium-enhanced images demonstrate a multilobulated mass above the sella and normal pituitary extending into the interpeduncular cistern and into the prepontine cistern. The posterior portion above the sella is solid (arrowheads), whereas the remainder is cystic with faint rim enhancement. The T2-weighted axial image D shows the darker solid component (arrowheads) and the T2-bright cystic portions. Figure 52-17  Craniopharyngioma.

ACOUSTIC NEUROMAS/ VESTIBULAR SCHWANNOMA

Clinical Vignette A previously healthy 42-year-old Army chaplain noted that he could no longer hear well on the telephone using his left ear or understand a colleague when there was much ambient noise particularly from other conversations. In retrospect, he had experienced mild progressive ringing in this ear. Initially this was attributed to chronic loud noise exposure while assigned to an artillery brigade. Although this gradually worsened over several years, it was not until his telephone difficulties led him to test himself that he found he could no longer appreciate the sound of a watch ticking. He was otherwise totally well. His only abnormal finding on neurologic examination was grossly diminished hearing in his left ear. Audiometric examination revealed markedly decreased high-frequency appreciation and diminished speech discrimination in his left ear. Gadolinium MRI demonstrated a homogeneously enhancing 2 × 1.5-cm mass within the left cerebellar pontine angle. This emanated from his internal auditory canal and was associated with mild pontine distortion.

Demographics Acoustic neuromas are the second most common of the benign brain tumors. These comprise approximately 6–8% of all primary intracranial neoplasms. There is a 2% incidence within the general population. Most commonly, acoustic neuromas present between ages 40 and 60 years. With the exception of patients who have genetically determined neurofibromatosis type II, it is unusual to see a patient have an acoustic neuroma become clinically recognized before age 20 years. The non– genetically determined acoustic neuromas predominantly develop unilaterally. In contrast, those occasional patients with type II neurofibromatosis often have bilateral acoustic neuromas. These benign tumors arise from the Schwann cells of the vestibular nerve within the eighth cranial nerve complex (Fig. 52-18).

Clinical Presentation The classic history is illustrated in the above clinical vignette. Patients typically report a slowly progressive, unilateral hearing loss associated with tinnitus. This is consistent with the innate slow growth of a benign acoustic neuroma (also referred to as a vestibular schwannoma). Although acoustic neuromas arise from the vestibular portion of cranial nerve (CN) VIII, hearing loss is usually the most prominent symptom. Anatomically, CN-VII (facial) is closely

476  SECTION XI  •  Neuro-oncology

Facial (VII) nerve Superior vestibular nerve Inferior vestibular nerve

Tumor

II

Tumor

I

Cochlear nerve Porus acusticus

Stimulus

Vestibular nerve Facial (VII) nerve

III IV V

I

II

III

IV

Left ear V

Right ear Delay

Internal auditory meatus (opened) Small neurinoma arising from superior vestibular nerve in internal auditory meatus and protruding into posterior fossa

Brainstem auditory evoked response (BAER) in patient with acoustic neurinoma on right side. There is delay in action potentials of cochlear nerve (wave I) and cochlear nuclei (wave II) on affected side.

Neurofibromatosis, Type II

A

B

V VII VIII IX X

C

Large acoustic neurinoma filling cerebellopontine angle, distorting brainstem and cranial nerves V, VII, VIII, IX, X

D

(A-C) Axial and coronal (D) T1-weighted post–gadoliniumenhanced images demonstrating bilateral vestibular schwannomas (arrows) and multiple dural-based meningiomas (arrowheads). Both types of tumors enhance avidly. Figure 52-18  Acoustic Neuroma.

related to CN-VIII; however, it is almost unheard of for an acute facial nerve palsy to be the initial presenting symptom of an acoustic neuroma. Because of the eighth nerve’s relation to the vestibular nerve within the cerebellopontine angle, adjacent to the brainstem and cerebellum, patients with very large acoustic neuromas may also have gait instability and sometimes associated headaches, but these individuals do not present with acute vertigo. Later on an acoustic neuroma may sometimes lead to pressure on either the trigeminal (fifth) cranial nerve or its adjacent brainstem, affecting CN-V function with a resultant ipsilateral facial sensory loss and a diminished corneal reflex. Occasionally very large tumors may impair the CSF circulation near the fourth ventricle, leading to hydrocephalus. During clinical examination, cranial nerve evaluation is the key to this diagnosis and of utmost importance. Hearing loss

from CN-VIII involvement is the hallmark finding for acoustic neuromas. Lateral gaze nystagmus is occasionally noted when testing extraocular movements. Larger tumors may cause CN-VII and CN-V impairment as previously summarized. It is most unusual to have any lower cranial nerve involvement or clinically significant enough brainstem compression to lead to either a hemiparesis or hemisensory loss.

Diagnostic Studies MRI is the primary diagnostic modality. Its clarity, resolution, and ability to scan in multiple planes allow for three-dimensional assessment. Because lesion size and its relation to adjacent neurologic structures, such as the pons and various cranial nerves, often determine treatment, MRI is also a therapeutically very



CHAPTER 52  •  Brain Tumors  477

Chordoma of sacrum bulging into pelvis, compressing rectum and other pelvic organs, as well as vessels and nerves

This mass is bright on a similar Axial T1-weighted image shows replacement of T2-weighted image (arrowheads). normal marrow fat (arrowheads).

Chordomas of clivus compressing pons and encroaching on sella turcica and sphenoid sinus Figure 52-19  Chordomas.

crucial investigational modality. Typically, these well-demarcated, homogeneously enhancing tumors arise within the cerebellar pontine angle and extend into the internal auditory canal (see Fig. 52-18).

Treatment Surgery is the traditional and primary therapeutic modality; stereotactic radiosurgery is occasionally used. Acoustic neuromas often grow slowly. It is reasonable to observe some tumors temporally, if clinically warranted, particularly with elderly patients presenting with unilateral hearing loss who also have multiple other medical issues. Often the better part of valor here is to just follow the patient with serial imaging. When MRI evidence demonstrates significant tumor growth or patients have progressively worsening symptoms, especially in addition to hearing loss, surgical intervention is indicated. Surgical resection of acoustic neuromas is often performed concomitantly using both neurosurgery and otorhinolaryngology specialists. The surgical goal is tumor resection and preservation of CN-VII and CN-VIII function when at all possible. This approach is particularly important with large-volume tumors exhibiting brainstem compression. Hearing preservation in patients with these large acoustic neuromas is often impossible because the cochlear nerve becomes indistinguishable from the tumor. Success rates for hearing preservation vary directly

with tumor volume. When CN-VII is densely adherent to the tumor capsule, a subtotal resection is often indicated, because facial nerve preservation is more important than complete surgical removal. Stereotactic radiosurgery involves a single nonsurgical treatment using high-dose radiation to a precisely localized threedimensional volume. This modality can control approximately 80–85% of acoustic tumors. It retains many of the same risks as conventional surgery but is an excellent option for patients with small tumors (2–3 cm) who have no useful hearing. Control of tumor growth is achieved and operative risks are avoided. With improved imaging, acoustic neuromas are being detected earlier; therefore, greater potential exists to achieve a complete cure early on in the natural history of the acoustic neuroma.

OTHER BENIGN INTRACRANIAL TUMORS Chordoma These are very rare usually benign tumors that have embryologic elements similar to intervertebral disks. Typically, chordomas develop either on the clivus of the skull base or the sacrum (Fig. 52-19). Intracranial chordomas arise from within the skull bone and cause local destruction. Concomitantly these tumors enter the intradural space, where they sometimes affect the brainstem and cranial nerves.

478  SECTION XI  •  Neuro-oncology

Tumor compressing mesencephalic tectum and corpora quadrigemina, occluding cerebral aqueduct (of Sylvius), and invading 3rd ventricle

Pineoblastoma. Axial FLAIR and sagittal T1-weighted gadolinium-enhanced images show a large mass in the pineal region, bright on FLAIR imaging, heterogeneous after gadolinium enhancement, compressing the aqueduct with enlargement of the third and lateral ventricles.

Parinaud syndrome: paresis of upward gaze, unequal pupils, loss of convergence

Anatomic aspects of exposure Internal cerebral v. Skull

Great cerebral v. (of Galen) Tentorium and straight sinus elevated by retractor

Diabetes insipidus in some patients

Sexual precocity in boys may occur

Basal v. (of Rosenthal) Approach Cerebellum Retractor Brainstem 3rd ventricle

Position of patient (undraped to show detail), surgeon, and microscope for resection of pineal region tumors

Tumor Cerebral aqueduct (of Sylvius)

Figure 52-20  Pineal Region Tumors.

The histology of typical chordomas is characterized by, large, mucus-filled cells called physaliferous cells. Very uncommonly, a few chordomas demonstrate features of frank malignancy. Additionally their aggressive local invasion of bone mimics a locally malignant process. The tumors that lead to significant bony destruction often recur locally at a high rate, thus making a surgical cure difficult to achieve. Nevertheless, surgical resection is often used initially, but complete resection is often impossible because of local anatomic constraints. Although radiation therapy is generally used, the role of this modality for treat­ ment of residual tumor is unclear. Radiosurgery and proton beam irradiation have been proposed, but their benefit is also uncertain. Chemotherapy is not of value for treatment of chordomas.

Pineal Region Tumors Tumors occurring in the region of the pineal gland are uncommon, comprising approximately 1% of intracranial tumors. These neoplasms, having a histologically mixed benignancy, include germ cell tumors, glial neoplasms, and pineal parenchyma tumors (Fig. 52-20). Germ cell origin tumors are the most common, usually occurring in younger patients. Gliomas can arise from within the pineal gland itself or from the glial cells in the surrounding tissue. In this region, glial tumors tend to be of lower grade. Tumors arising from the pineal parenchyma comprise approximately 20% of pineal region tumors. These neoplasms are further classified into pineoblastomas and pineocytomas. Pineoblastomas are poorly differentiated



CHAPTER 52  •  Brain Tumors  479

A

Subependymoma of anterior horn of left lateral ventricle obstructing interventricular foramen (of Monro), thus producing marked hydrocephalus

Colloid cyst of 3rd ventricle and surgical approach via right prefrontal (silent) cerebral cortex. May also be approached through corpus callosum (arrow). Note enlarged lateral ventricles (posterior view).

B

Colloid cyst. (A) Axial, FLAIR and (B) coronal, T1-weighted gadolinium-enhanced images demonstrate a round cystic mass in the region of the foramina of Monro, with dilatation of the lateral ventricles. The signal characteristics are variable. This cyst is hypointense on T2-weighted images and bright on T1weighted imaging, with minimal peripheral enhancement.

Figure 52-21  Intraventricular Tumors.

tumors that can spread throughout the cerebrospinal fluid pathways or directly into adjacent brain parenchyma. Pineocytomas are usually well-encapsulated cellular tumors that do not invade surrounding tissue. A mixed form of pineal parenchymal tumor contains features of both pineocytoma and pineoblastoma. Teratomas, embryonal carcinomas, endodermal sinus tumors, and choriocarcinomas are also found in the pineal region. With the increasing use of MRI, asymptomatic pineal region cysts are identified more commonly. These cysts are usually incidental findings and rarely require any treatment. Serial MRI scans are used to track any growth over time.

Colloid Cysts These are histologically benign third ventricle tumors that arise from embryologic development remnants. The cells lining the walls of the cyst are ciliated. Third ventricular lesions of this type typically do become symptomatic during adulthood but can be seen in children. Posturally precipitated headaches, with concomitant symptoms and signs of hydrocephalus are the most common clinical presentations for colloid cysts. Because of their inherent intraventricular location, these cysts lead to CSF obstruction at the foramina of Monro (Fig. 52-21). Colloid cysts occasionally are associated with sudden death presumably from an acute hydrocephalus; however, most patients present with a more gradual temporal profile. Although the diagnosis is typically suggested by recurrent posturally triggered headaches, MRI or CT is ideal for confirming the presence of a cystic-appearing intraventricular mass. Treatment of symptomatic colloid cysts is usually surgical, and complete resection is often possible. Care must be exercised during surgical resection because the fornix, adjacent to the tumor, can be injured, resulting in severe memory impairment. If surgery for resection is not possible, CSF diversion through shunting can often relieve the symptoms of hydrocephalus.

With the increased use of MRI, many more cystic tumors within the third ventricle are being described. These asymptomatic lesions are followed with serial scans; treatment is reserved for those patients whose cysts increase in size.

DIFFERENTIAL DIAGNOSIS Pseudotumor Cerebri/Idiopathic Intracranial Hypotension, Intracranial Hypotension, and Other Brain Lesions

Clinical Vignette An obese 42-year-old woman presented with a 2-month history of increasingly severe headaches and intermittent double vision. Her headaches were exacerbated by postural changes, particularly bending forward or jarring in the car. Bilateral limitation of adduction of her eyes compatible with sixth cranial nerve paresis and modest papilledema (Fig. 52-22) were noted on neurologic examination. Brain imaging demonstrated diminished size of her lateral ventricles. Cerebrospinal fluid (CSF) pressure was 350 mm CSF (normal < 180 mm CSF); it was otherwise normal.

This case is representative of a rather uncommon syndrome known as idiopathic intracranial hypertension, i.e., pseudotumor cerebri (PTC). This usually occurs in obese young women who are otherwise healthy. Clinically PTC is primarily characterized by progressively severe, poorly defined headaches, often with diplopia. Transient visual obscurations and pulsatile tinnitus may also occur. On neurologic examination these patients are typically awake, alert, have papilledema, sometimes a lateral rectus muscle weakness, but no focal neurologic deficits. By definition MRI is normal or demonstrates small lateral ventricles. PTC by definition is associated with increased CSF pressure (250–500 mm CSF).

480  SECTION XI  •  Neuro-oncology

Obese young woman: persistent headache

Papilledema: nasal blurring of optic disc vessels Often related to pregnancy; menstrual disturbances; hypervitaminosis A; use of steroids, tetracycline, or nalidixic acid; chronic otitis media with dural sinus occlusion; endocrinopathy Addison or Cushing disease, hypoparathyroidism

Concentrically contracted visual fields, large blind spots

Cerebrospinal fluid pressure elevated

Figure 52-22  Pseudotumor Cerebri.

Although idiopathic PTC has no identifiable etiology, certain predisposing factors need to be considered, including oral contraceptives, corticosteroids, estrogens and progestational therapies, NSAIDs, hypervitaminosis A, various antibiotics (tetracycline, minocycline, nitrofurantoin, ampicillin, or nalidixic acid), anesthetic agents (ketamine and nitrous oxide), amiodarone, and perhexiline. Other neurologic disorders may occasionally present with a PTC clinical picture. These include leptomeningeal diseases such as chronic infectious or granulomatous processes, that is, tuberculosis, metastatic cancer or lymphoma seeding, cerebral venous sinus obstruction, and various endocrinologic disorders, for example, myxedema, hypoparathyroidism, and Addison and Cushing diseases. There are very rare reports of a PTC picture presumed to be related to extremely elevated CSF protein levels, particularly with Guillain–Barré syndrome or primary spinal cord malignancies.

Treatment Discontinuation of an offending medication will reverse the PTC syndrome on the rare occasion such is identified. Most importantly one needs to be concerned by the fact that chronic increased intracranial pressure leads to loss of visual acuity. This is secondary to swelling of the optic nerve head, that is, papilledema. It is measured by frequent and formal visual field testing to identify increasing size of the blind spots. This is essential to prevent permanent visual loss with PTC. Potential treatments

include weight loss, low-salt diet, diuretics, and symptomatic headache control. When PTC continues to evolve with progressive visual compromise, more aggressive therapy is indicated, including optic nerve sheath fenestration or one of the various CSF shunting procedures.

Intracranial Hypotension (Low-CSF-Pressure Syndrome)

Clinical Vignette A vigorous previously healthy 60-year-old physician, who had recently developed severe depression, requiring both a serotonin reuptake inhibitor as well as unilateral electric shock therapy (EST), developed increasingly severe posturally exacerbated headaches. When these were greatly exacerbated while he was a passenger in a small float plane as it landed bouncing over the water, he went to a neurologist. His examination was normal. Postgadolinium MRI demonstrated leptomeningeal enhancement but no mass lesions. CSF pressure was too low to measure. No known relation with the EST was identified. He then recalled having a relatively severe closed head injury 3 weeks earlier when he forcefully struck his forehead on an unexpectedly low-set barn door frame. A 20-mL extradural blood patch was empirically injected at his mid-lumbar spine. The headaches gradually and totally cleared within 2 weeks.



CHAPTER 52  •  Brain Tumors  481

Other Intracranial Lesions

A. Axial FLAIR image with dural thickening.

Subdural hematomas, herpes encephalitis, brain abscess, and arteriovenous malformations may all have a clinical presentation similar to a brain tumor. There are other rare disorders both of demyelinating nature that require consideration in the differential diagnosis of brain tumors. Occasional patients have MRI findings mimicking a malignant glioma, but stereotactic biopsy demonstrates a primary monofocal acute inflammatory demyelination (see Chapter 46). These lesions usually are self-limited and occur in the setting where there is no prior clinical or MRI evidence of multiple sclerosis. Fortunately these are often responsive to corticosteroids. Subsequently, new lesions may appear in different portions of the cerebral cortex. An acute disseminated encephalomyelitis (ADEM) and acute hemorrhagic leukoencephalopathy (AHL) are two acute postinfectious demyelinating disorders; the former is more likely to respond to corticosteroids and the latter frequently has a fulminate course (see Chapter 47). Progressive multifocal leukoencephalopathy (PML) may also present in a fashion similar to a brain tumor in immunocompromised hosts receiving long-term immunosuppressive therapy or in patients with HIV (see Chapter 51).

FUTURE DIRECTIONS

B. Axial T1-weighted, gadolinium-

enhanced image with striking enhancement of the thickened dura.

Figure 52-23  Intracranial Hypotension.

Classic low-CSF-pressure headaches are severe, exacerbated by postural factors, and often mimic the ball valve effect seen in some intraventricular brain tumors. Most commonly, these occur subsequent to a diagnostic lumbar puncture, spinal anesthesia, or a seemingly benign closed head injury. MRI with gadolinium is essential to the diagnosis (Fig. 52-23). When there is no history of a spinal tap or significant head trauma, this clinical setting, as well as the MRI, somewhat mimics various leptomeningeal neoplastic or inflammatory lesions. The MRI imaging with low pressure headache syndrome has a smooth enhancement in contrast to serpiginous irregular enhancement seen with neoplastic infiltration. The CSF analysis primarily helps make this differentiation. Occasionally introduction of a radioisotope into the CSF will identify a source of CSF leak that may require surgical repair. In many of these instances, no site of potential spinal fluid leak is identified. As in the above vignette, a spinal blood patch can provide relief and a therapeutic diagnosis; however, it is not universally successful and in rare instances the patient may have permanent incapacitation not being able to raise his/her head, preventing one from pursuing an occupation or even many routine activities of daily living.

Treatment of benign intracranial tumors has improved with better MRI imaging and the development of new surgical techniques that exploit bone removal rather than brain manipulation. These skull base techniques allow for exposure and resection of tumors in previously inaccessible locations within the skull. Intraoperative monitoring of cranial nerve function is being used more frequently to limit the morbidity of these operations. Improvements in stereotactic radiosurgery continue to allow for tumor growth control while causing fewer radiation adverse effects. Further research into the relation of hormonal receptors in meningiomas may someday allow for a medical means of controlling these tumors. ADDITIONAL RESOURCES Ahsan H, Neugut AI, Bruce JN. Trends in incidence of primary malignant brain tumors in USA, 1981-1990. Int J Epidemiol 1995;24(6):10781085. Berger MS, Hadjipanayis CG. Surgery of intrinsic cerebral tumors. Neurosurgery. 2007 Jul;61(Suppl. 1):279-304. Binder DK, Horton JC, Lawton MT, et al. Idiopathic intracranial hypertension. Neurosurgery 2004;54:538-551. Black PM. Meningiomas. Neurosurgery 1993;32:643-657. Castrucci WA, Knisely JP. An update on the treatment of CNS metastases in small cell lung cancer. Cancer J 2008 May-Jun;14(3):138-146. Ciric I. Long-term management and outcome for pituitary tumors. Neurosurg Clin N Am 2003;14:167-171. Daumas-Duport C, Scheithauer BW, O’Fallon J, et al. Grading of astrocytomas: a simple and reproducible method. Cancer 1988;62:2152-2165. Dietrich J, Norden AD, Wen PY. Emerging antiangiogenic treatments for gliomas—efficacy and safety issues. Curr Opin Neurol 2008 Dec;21(6): 736-744. Gutrecht JA, Berger JR, Jones HR, et al. Monofocal acute inflammatory demyelination (MAID): a unique disorder simulating brain neoplasm. South Med J 2002;95:1180-1186.

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Karim AB, Afra D, Cornu P, et al. Randomized trial on the efficacy of radiotherapy for cerebral low-grade glioma in the adult: European Organization for Research and Treatment of Cancer Study 22845 with the Medical Research Council study BRO4: an interim analysis. Int J Radiat Oncol Biol Phys 2002;52(2):316-324. Kennedy PG. Viral encephalitis: causes, differential diagnosis, and management. J Neurol Neurosurg Psychiatry 2004;75(Suppl. 1):i10-i15. Koss SA, Ulmer JL, Hacein-Bey L. Angiographic features of spontaneous intracranial hypotension. AJNR Am J Neuroradiol 2003;24:704-706. Larijani B, Bastanhagh MH, Pajouhi M, et al. Presentation and outcome of 93 cases of craniopharyngioma. Eur J Cancer Care (Engl) 2004;13: 11-15. Maarouf M, Kuchta J, Miletic H, et al. Acute demyelination: diagnostic difficulties and the need for brain biopsy. Acta Neurochir (Wien) 2003; 145:961-969. MacFarlane R, King TT. Acoustic neurinoma: vestibular schwannoma. In: Kaye AH, Larz Jr ER, editors. Brain Tumors. Philadelphia, Pa: Churchill Livingstone; 1995. p. 577-622. Mason WP, Cairncross JG. Invited article: the expanding impact of molecular biology on the diagnosis and treatment of gliomas. Neurology 2008 Jul 29;71(5):365-373. Mathiesen T, Grane P, Lindgren L, et al. Third ventricle colloid cysts: a consecutive 12-year series. J Neurosurg 1997;86:5-12.

Menezes AH, Gantz BJ, Traynelis VC, McCulloch TM. Cranial base chordomas. Clin Neurosurg 1997;44:491-509. Mokri B. Headaches caused by decreased intracranial pressure: diagnosis and management. Curr Opin Neurol 2003;16:319-326. Ohgaki H. Epidemiology of brain tumors. Methods Mol Biol 2009;472: 323-342. Prados MD, Scott C, Curran Jr WJ, et al. Procarbazine, lomustine, and vincristine (PCV) chemotherapy for anaplastic astrocytoma: A retrospective review of radiation therapy oncology group protocols comparing survival with carmustine or PCV adjuvant chemotherapy. J Clin Oncol 1999 Nov;17(11):3389-3395. Rapport RL, Hillier D, Scearce T, et al. Spontaneous intracranial hypotension from intradural thoracic disc herniation: case report. J Neurosurg 2003;98(Suppl.):282-284. Raschilas F, Wolff M, Delatour F, et al. Outcome of and prognostic factors for herpes simplex encephalitis in adult patients: results of a multicenter study. Clin Infect Dis 2002;35:254-260. Tentori L, Graziani G. Recent approaches to improve the antitumor efficacy of temozolomide. Curr Med Chem 2009;16(2):245-257. Ullrich RT, Kracht LW, Jacobs AH. Neuroimaging in patients with gliomas. Semin Neurol 2008;28(4):484-494.

Spinal Cord Tumors

53 

Peter K. Dempsey and Lloyd M. Alderson

T

he most common spinal cord tumors are metastatic extradural lesions usually but not always occurring in patients with already identified malignancies, either cancers or lymphomas. Their presentation is often relatively acute, usually associated with focal back and/or radicular pain. On occasion, these lesions are the initial clinical manifestation of a heretofore unsuspected systemic malignancy. In contrast, primary intradural spinal cord tumors occur infrequently; typically their presentation is a relatively subtle one, ingravescent in temporal profile. Spinal cord and spinal column tumors are best classified within two categories: extradural, occurring outside of the dura, and intradural, contained within the dura mater (Table 53-1; Fig. 53-1). Intradural tumors are further categorized as extramedullary or intramedullary, depending on their relationship to the spinal cord. Intradural extramedullary tumors, usually meningiomas or schwannomas, generally arise outside of the spinal cord parenchyma. These are initially clinically silent; however, with time these tumors surreptitiously enlarge. Once a critical mass is reached, spinal cord compression occurs and symptoms develop. In contrast, intradural intramedullary tumors, such as gliomas and ependymomas, originate within parenchyma of the spinal cord. As these intramedullary malignancies primarily expand, important neurologic pathways and cell populations are subsequently compromised and eventually destroyed. Extradural tumors generally are derived from metastatic lesions to vertebral bodies with extension into the epidural space, causing external compression of the thecal sac and its contents. Primary bony vertebral tumors also occur, both malignant, such as myeloma, and benign, including hemangiomas and osteoid osteomas.

EXTRADURAL SPINAL TUMORS Clinical Vignette A 62-year-old postal carrier presented with midthoracic pain and rapidly progressive weakness and numbness in both legs and difficulty initiating his urine stream. During the preceding 6 weeks, he intermittently awakened with midthoracic vertebral pain that increasingly radiated to his epigastrium. This was particularly precipitated by lifting, bending, or straining at stool. An initial gastrointestinal evaluation was normal. Twenty-four hours before admission, he began to experience progressive difficulty standing, walking, and voiding. The morning of this evaluation, he was unable to get out of bed on his own and was totally unable to void. During the past 3 months, he had noted an increasingly irritating cough; he was a 60-pack-year smoker. Neurologic examination demonstrated a T9 “cord level” to both pinprick and temperature. Muscle stretch reflexes were absent at the knees and ankles, and plantar stimulation was flexor. There was mild tenderness to palpation over the

lower thoracic spine. He became incontinent of urine. Rectal sphincter tone was lax. Spinal radiographs revealed destruction of the T9 vertebral body. Magnetic resonance imaging (MRI) demonstrated a soft tissue mass involving most of the T9 vertebral body, extending into the pedicle, with epidural extension of the tumor into the spinal canal leading to marked compression of the spinal cord. Immediate dexamethasone and subsequent radiation therapy was unsuccessful in reversing his clinical course. Chest radiograph (Fig. 53-2) demonstrated a left main stem bronchus tumor that on biopsy proved to be a primary small cell lung cancer. Spinal neoplasms are predominantly secondary to metastatic cancer. This occurs in up to one third of cancer patients. Lung, breast, prostate, and lymphoma are the most common metastatic lesions leading to spinal cord compression.

CLINICAL PRESENTATION Severe focal vertebral pain is frequently the presenting symptom of a metastatic spinal cancer (Fig. 53-2). Unfortunately, back pain is such a ubiquitous complaint that the serious nature of a newly occurring pain is often not appreciated even when there is no history of recent trauma. Sometimes, it is difficult to distinguish pain of a metastatic spinal tumor from the much more common mechanical, degenerative, or osteoarthritic musculoskeletal lower back and/or nerve root disorders. However, pain of metastatic spinal cancer origin is often persistent, frequently unrelated to posture, and tends to increase at night. In contrast to more common mechanical back pain, this pain can be of more recent origin. Progressive neurologic symptoms often vary and are related to the precise level of spinal column involvement; typically the temporal profile is relatively rapid. Tumors at the cervical and thoracic spinal cord levels present with progressive weakness, numbness, and sphincter dysfunction at levels below the tumor. Sphincter difficulties are nonspecific symptoms per se that may develop with tumors at any spinal level. On occasion, bladder and bowel dysfunction per se may be the initial presenting symptom related to a conus medullaris tumor at the distal tip of the spinal cord. The essential message is that whenever sphincter problems develop in a patient with a known cancer, one needs to be alert to the potential of a spinal metastasis. Examination usually reveals hyperreflexia, Babinski signs, and other long tract signs at spinal levels below the tumor involvement. When evaluating patients with recent-onset sphincter difficulties and suspicion for a metastatic lesion, it is important to recognize that differentiation of conus medullaris lesions, at the spinal cord tip, versus those within the cauda equina may be difficult. Classically when the clinical findings are symmetric and relatively equally involving both lower extremities, the

484  SECTION XI  •  Neuro-oncology

Table 53-1  Classification of MRI Abnormalities* Extradural Extramedullary

Intradural Extramedullary

Intradural Intramedullary

Disc disease Metastatic carcinoma Lymphoma Sarcoma Plasmacytoma Primary bone tumor Scar Abscess Hemangioma Rare lesions Hemorrhage Neurilemmoma Meningioma Chordoma

Neurinoma Meningioma Intracranial tumor seeding Ependymoma Medulloblastoma Glioma Cauda equina lesions Scarring Hypertrophic neuropathy Rare lesions Lymphoma Metastasis Hemangioblastoma Lipoma Dermoid Epidermoid Cyst Clot

Syringomyelia Tumor Ependymoma Glioma Hemangioblastoma Myelitis Edema Lipoma Rare lesions Abscess Hematoma Varix with AVM Lymphoma Neuroblastoma Metastasis

*Dermoid or epidermoid, teratoma, lipoma, and cysts are often associated with spinal dysraphism. In this setting, many tumors are intradural, although they may involve all three areas.

Extradural tumors

Lymphoma invading spinal canal via intervertebral foramen, compressing dura mater and spinal cord

Intradural extramedullary tumors

Meningioma compressing spinal cord and distorting nerve roots

Intramedullary tumors

Astrocytoma exposed by longitudinal incision in bulging spinal cord

Figure 53-1  Classification of Spinal Tumors.

conus medullaris is much more likely the site of the specific pathology. In contrast, cauda equina lesions often lead to an asymmetric distribution of signs and symptoms because not all nerve roots within the cauda equina are equally affected. Typically, the course of extradural metastatic spinal tumors is more rapid than intradural tumors. It is not unusual for these lesions to have an almost precipitous onset, often producing rapidly evolving motor and sensory deficits within just a few hours to a day or so (Fig. 53-3). A prior diagnosis of either a cancer or a lymphoma will alert the astute clinician to the precise pathophysiologic nature of the spinal lesion. However,

occasionally a spinal metastasis may be the initial presentation of a metastatic malignancy.

DIAGNOSTIC APPROACH MRI is the standard for evaluating potential metastatic spine lesions, especially those with evolving cord compression. When an MRI is contraindicated, such as with a patient who has a pacemaker, CT myelogram is still a very useful and valid study. An initial preliminary spinal tap is best avoided in these patients as such can change pressure dynamics when there



CHAPTER 53  •  Spinal Cord Tumors  485

Common primary sites, noted on history or examination Breast

Prostate

Melanoma (skin or mucous membrane) Lymphoma (may be primary)

Lung

X-ray film showing destruction of pedicle and vertebral body by metastatic carcinoma

Sagittal T1-weighted, gadolinium-enhanced image shows enhancement within the vertebral lesions and epidural extension with spinal cord compression at T10 (arrow).

Bone scan showing multiple metastases Figure 53-2  Extradural Metastatic Spinal Tumors.

Back pain: onset acute or gradual

Progression over minutes, h

Numbness of limbs

ours

fe w

Urinary urgency

d s ay

11 12 1 2 10 3 9 8 4 7 6 5

, or

Weakness

Figure 53-3  Clinical Profile: Acute Spinal Cord Decompensation with an Epidural Tumor.

Paralysis (may occur without premonitory symptoms)

486  SECTION XI  •  Neuro-oncology

Albumin



 1 2 Malignant myeloma cells in biopsy specimen of bone marrow

Multiple myeloma

 spike on serum electrophoresis

Bence Jones protein in urine in 60% of cases (precipitates at 45° to 60°C, redissolves on boiling, and reprecipitates on cooling at 60° to 45°C) 55ûC 100ûC 55ûC

A

B

Metastatic tumor. (A) Sagittal T1weighted image demonstrates loss of normal marrow fat at multiple levels. (B) Sagittal T1-weighted, gadoliniumenhanced image shows enhancement within the vertebral lesions and epidural extension with spinal cord compression at T10 (arrow).

C

D

E

Epidural hematoma. (C) T1-weighted sagittal image shows a vague posterior epidural mass better seen on D. (D) T2-weighted image extending from C2 into the thoracic region.

F

Epidural abscess. Sagittal T1-weighted images without (E) and with (F) gadolinium enhancement demonstrate an extensive posterior epidural process from T6 to T11. Enhancement of the granulation tissue allows appreciation of nonenhancing focal pus collections.

Figure 53-4  Extradural Primary Malignant Spinal Tumors.

is an obstructing focal cord lesion. If a spinal tap is performed, this study can precipitate a rapid worsening of the patient’s neurologic deficits. If a primary cancer has not been previously found, a histologic diagnosis becomes mandatory to confirm the nature of the lesion. In some instances, there is a primary bony malignancy such as multiple myeloma originating within the vertebrae per se (Fig. 53-4). Today percutaneous CT-guided needle biopsy is often the most useful procedure if no primary is immediately apparent such as occurred in this chapter’s opening vignette, where a routine chest radiograph led to a diagnostic lung biopsy. When there is no evidence of a primary lesion identified, an open surgical procedure, such as neurosurgical spinal cord decompression with a conjoint biopsy, is very important.

TREATMENT AND PROGNOSIS There are three primary indications for treatment of spinal column metastatic disease: (1) to prevent further spinal cord destruction, (2) to prevent progression of the neurologic deficits, and (3) to control pain. Typically large-dose corticosteroids, that is, 10–20 mg of dexamethasone, followed by 4–6 mg every 4–6 hours, are administered at diagnosis and continued throughout the initial treatment stages for their protective effect on the neural elements. Focused radiation therapy and/or surgical decompression are the two primary treatment modalities for epidural metastases. When the patient’s neurologic examination demonstrates serious

neurologic compromise, radiation therapy may be the initial treatment of choice, particularly depending on the identification of the specific pathology. This is administered locally in multiple fractions that are precisely directed to the involved vertebrae. Pain relief often occurs relatively rapidly within just a few days after commencement of the radiation therapy. Unfortunately some tumors such as renal cell cancer are radiotherapy-resistant tumors. Here the symptoms typically evolve progressively despite radiation therapy. In this setting, surgery is often indicated once the radiotherapy per se is completed. On occasion, patients who present with specific neurologic symptoms and signs are best treated with surgery. This provides for rapid decompression of the neural elements and preserves previously unaffected neurologic function. Surgical intervention generally requires removal of as much tumor as possible. In many instances, when spinal column destruction has caused significant spinal instability, fusion and/or grafting is initially required followed by subsequent radiotherapy to the area. Prognosis for patients with metastatic disease to the spine depends on their clinical status upon presentation. Individuals who have presented with a severe neurologic deficit such as paraplegia existing at least 24–36 hours often do not regain significant neurologic function. However, many patients who present with acute deterioration, still retaining some distal neurologic function, who undergo rapid evaluation and treatment often experience improvement. Very occasionally, one finds a few types of primary benign bony vertebral tumors. Although histologically these are not



CHAPTER 53  •  Spinal Cord Tumors  487

Osteoid osteoma

Axial CT demonstrates coarsened trabeculae interspersed with fat lucency. Intraosseous hemangioma involving whole vertebral body with small epidural extension

Hemangioma

Axial T2-weighted fast spin echo image demonstrates mixed intensity pattern within vertebral body with left anterolateral epidural extension (arrow). Intraosseous hemangioma with small epidural extension (arrow)

Axial T1-weighted fast spin echo post–gadoliniumenhanced image shows a heterogeneous but generally bright signal pattern within the vertebral body similar to the nonenhanced T1 image; however there is enhancement of the epidural component (arrow). Intraosseous hemangioma with small epidural extension (arrow)

Figure 53-5  Extradural Primary Benign Spinal Tumors.

malignant as are most extradural tumors, these lesions may reach a critical mass, causing vertebral collapse and spinal cord compression (Fig. 53-5). Usually these benign tumors have a less aggressive clinical course; however, once they reach a critical mass, they may portend serious threat to spinal cord function. Uncommonly, surgical decompression is indicated.

INTRADURAL EXTRAMEDULLARY TUMORS Intradural extra-axial (extramedullary) tumors originate within the dural sleeve of the spinal column but outside of the spinal cord, that is, intradural extramedullary. These lesions primarily arise within the leptomeninges or the nerve roots. Additionally, one may find meningiomas within this age group.

Clinical Vignette This 41-year-old woman noted the occasional appearance of tingling in her right leg that was particularly prominent when she played tennis. She had no significant back pain. Her initial detailed neurologic examination was perfect. MRI of the lumbosacral spine was normal. A follow-up appointment was scheduled for 2 months. However, within just a few weeks, she noted persistent right leg numbness particularly present when she shaved her leg. On self-testing, she became cognizant of diminished touch sensation in a pre-tibial distribution. Lumbar spine MRI was normal.

Sub­sequently, her walking began to be limited as her left foot seemed to turn in after walking a few blocks. Repeat neurologic examination demonstrated a slightly spastic gait, subtle weakness of the left iliopsoas, more brisk muscle stretch reflexes on the left, a left Babinski sign, and a subtle cord level to pin and temperature sensation at T6 on the right. MRI confirmed the presence of a large intradural extramedullary tumor compressing the spinal cord. An encapsulated benign meningioma was surgically removed. She had an excellent recovery with no clinical residua.

There was a seeming paradox here in that even when the patient developed clinical symptoms, her neurologic examination was initially normal. And then as her symptoms became more specific and subtle abnormalities appeared on neurologic examination, her MRI demonstrated very marked spinal cord compression with a very significant-sized tumor. The clinical temporal profile of meningiomas is to gradually enlarge, subtly compressing the spinal cord. This tissue is amazingly resilient when the pathologic process is a very ingravescent one. Here the initial symptoms were relatively benign, with intermittent leg numbness precipitated by exercise and body heat. Such a setting, in the face of a normal lumbar MRI, suggested the possibility of early multiple sclerosis. Continued observation was therefore important, as were patient instructions to call with any new symptomatology and return for follow-up within a few months. On this occasion,

488  SECTION XI  •  Neuro-oncology

Intradural extramedullary tumor (meningioma) compressing spinal cord and deforming nerve roots

Dumbbell tumor (neurilemmoma) growing out along spinal nerve through intervertebral foramen (neurofibromas of von Recklinghausen disease may act similarly)

Foraminal neurolemmoma seen on axial T1-weighted, gadolinium-enhanced image (arrowheads) Thoracic meningioma: axial and sagittal T1-weighted, gadolinium images show that the enhancing mass occupies the right anterior 70% of the spinal canal A. Meningioma. Meningioma with a meningothelial pattern showing cells with syncytial features in lobulated groups (H&E, original magnification 200X)

B. Schwannoma (neurilemmoma). Antoni B pattern in a schwannoma showing spindle cells arranged in fascicles (H&E, original magnification 200X)

Figure 53-6  Intradural Extramedullary Primary Spinal Tumors.

subsequent neurologic examination demonstrated a subtle sensory cord level and contralateral corticospinal dysfunction, typical of a classic Brown–Sequard syndrome indicating a specific level of spinal cord dysfunction (see Chapter 44). Focused spinal MRI at a higher level led to the diagnosis of this treatable lesion. Intradural extramedullary tumors are most commonly meningiomas (Fig. 53-6A) arising from within the dura per se, or are nerve sheath tumors. The latter are classified into two main groups, schwannomas, about 65% (Fig. 53-6B), and neurofibromas. Both often have a similar gross appearance and require microscopic analysis for differentiation. Neurofibromas have less dense cellular structure (Antoni B pattern) and often contain nerve elements. Usually benign, these lesions occur as a solitary finding or as multiple nodules throughout the body. Type I neurofibromatosis (von Recklinghausen disease) is a familial condition with two or more neurofibromas, associated neurocutaneous findings such as café-au-lait spots, and axillary freckling. Nerve sheath tumors such as schwannomas typically develop in middle-aged women. These lesions are benign, slowgrowing tumors that gradually lead to significant clinical symptomatology especially when these originate near the spinal cord. Type I neurofibromatosis (von Recklinghausen disease) is an autosomal dominant disorder often associated with optic gliomas, and Lisch nodules of the iris, along with certain skeletal abnormalities. Type II neurofibromatosis is most frequently associated with bilateral hearing loss due to neurofibromas of the eighth cranial nerve and are not associated with spinal cord

compression (see Chapter 52). Schwannomas have a dense pattern on microscopic analysis and may be found at the level of the nerve root.

Clinical Vignette A 36-year-old man reported a several-month history of progressive numbness on the lateral left foot. There was no associated back or leg pain, leg weakness, contralateral leg symptoms, or sphincter dysfunction. Neurologic examination demonstrated sensory loss to light touch and pin prick in the left S1 dermatome. He had full strength in both lower extremities. Muscle stretch reflexes were notable for an absent left Achilles reflex. An intradural mass was demonstrated at the left S1 level with MRI. There was no bony destruction, but the nerve root foramen was widened compared with the contralateral side. Given the progressive evolution of his clinical difficulties, he underwent surgical resection. Histologic analysis revealed a schwannoma, that is, a nerve sheath tumor.

CLINICAL PRESENTATION If a single nerve root is involved without invasion of the spinal cord or cauda equina, symptoms mimic a radiculopathy but often without the typical pain such as seen with either sciatica



CHAPTER 53  •  Spinal Cord Tumors  489

or Herpes zoster, that is, shingles. When these intradural extramedullary tumors develop, their initial symptoms are not always associated with significant neurologic signs at the first clinical evaluation. The evanescent symptoms may lead the clinician to consider the possibility of multiple sclerosis. Eventually, patients with a spinal lesion develop neurologic signs reflecting posterior column, spinothalamic, and corticospinal tract dysfunction.

At surgical exploration, an anaplastic spinal cord astrocytoma was found. A complete resection was not attempted because of the infiltrative nature of these tumors. Unfortunately, her symptoms continued to progress postoperatively, leaving her paraplegic and incontinent. These tumors do not respond to other treatment modalities such as radiation or chemotherapy.

TREATMENT The management of intradural, extramedullary nerve sheath tumors is dictated by the clinical scenario. Patients presenting with neurologic deficits are best managed by surgical resection. Often, intradural extramedullary nerve sheath tumors can be completely resected without a resultant neurologic deficit. The nerve fascicle upon which the tumor arises can usually be separated from other fascicles, avoiding nerve root injury. Although the fascicle is amputated when the tumor is resected, the patient often has no deficit. Radiation and chemotherapy are not required for these benign tumors. If an intradural extramedullary tumor is incidentally discovered, having no associated symptoms or signs; observation is often appropriate as many of these lesions have benign courses.

INTRADURAL INTRA-AXIAL TUMORS Tumors that originate and grow within the substance of the spinal cord are designated as intra-axial lesions, that is, “intradural, intramedullary” neoplasms (Fig. 53-7). These account for ~15% of all primary intradural tumors occurring in both children and adults.

Clinical Vignette A young woman, known to be an avid athlete, noted a few months’ history of right leg clumsiness; difficulty walking, often catching her foot; losing her balance; and experiencing some associated numbness. Her symptoms gradually increased. Subsequently, similar but milder symptoms developed in her left leg. There were no other associated symptoms and particularly no back or neck pain. Neurologic examination demonstrated mild right leg weakness, increased muscle stretch reflexes, a right Babinski sign, with loss of position and vibratory sensation in the right leg and diminished pinprick and temperature sensation on the left up to a T7 level. A T6 intra-axial spinal cord mass lesion was demonstrated with thoracic spine MRI. There was extensive T2 signal change within the cord, extending rostrally and caudally to the lesion. Further, similar imaging of the brain and distal spinal cord was normal as were visual evoked potentials. A lumbar puncture, performed to further exclude a primary central nervous system demyelinating process such as multiple sclerosis demonstrated an elevated protein level (96 mg/dL). However, there were no oligoclonal bands present. Cell counts were normal.

Although relatively quite rare, primary intradural intramedullary tumors always need to be considered in the differential diagnosis of any patient with possible primary spinal forms of multiple sclerosis. The majority of intramedullary spinal cord malignancies have a primary glial cell source: either an ependymoma or astrocytoma. Spinal cord astrocytomas are more infiltrative and nonencapsulated. Hemangioblastomas, lipomas, and dermoid, epidermoid, and metastatic tumors are among the other extremely rare intramedullary spinal cord tumors.

CLINICAL PRESENTATION Intramedullary tumors often present with progressive painless neurologic decline over several weeks. The above vignette demonstrated a classic Brown–Sequard syndrome characterized by unilateral hemimotor weakness, diminished position and vibratory sensation ipsilateral to the lesion, and loss of pain and temperature in the contralateral lower extremity. This classic presentation is typically seen in tumors predominantly occupying one side of the spinal cord. A “pure” Brown–Sequard syndrome is rare, as most patients with intradural intramedullary lesions have a mixed clinical presentation affecting both sides of the spinal cord (Fig. 53-7).

TREATMENT Total resection of ependymomas is occasionally a possibility as the surgeon may find that a tissue plane exists between the tumor and the normal spinal cord, allowing precise removal of the tumor. In contrast, astrocytoma cells have a tendency to more diffusely infiltrate other previously normal tissue, making any thought of a clean surgical extraction totally impossible. Additionally, the highly organized architecture of the spinal cord makes manipulation and resection of the malignant tissue extremely difficult if not impossible. Therefore, the current recommendation is to perform a primary biopsy and possibly a limited resection when dealing with presumed astrocytomas. Recent technological developments in the operating room, including ultrasound, intraoperative MRI, and ultrasonic aspirators, may eventually lead to improved surgical outcomes. Although both chemotherapy and radiation therapy are advocated for treatment of spinal cord astrocytomas, the results are no more than equivocal. In contrast, ependymomas that are thought to have been completely resected do not require radiation and chemotherapy. Often the best course for such a patient is a period of careful observation with clinical and MRI follow-up.

490  SECTION XI  •  Neuro-oncology

Astrocytoma on gadoliniumenhanced T1-weighted image with diffuse cord enlargement and focal enhancement (arrow)

Intramedullary tumor and myelogram showing widening of spinal cord

Tumor of filum terminale compressing cauda equina: enlarged vessels feed tumor

Ependymoma of filum with cyst: sagittal T1-weighted, gadolinium-enhanced image with large, moderately enhancing mass (arrowheads) and cyst distal to it (thin arrows)

Intramedullary metastases: multiple enhancing masses within the spinal cord (arrows) Figure 53-7  Intradural Intramedullary Primary Spinal Cord Tumors.

FUTURE DIRECTIONS The major issue and challenge relates to finding medically successful treatment modalities for the primary glial cell spinal tumor groups, particularly the astrocytomas. Advances in their treatment are occurring in several areas. Imaging, such as MRI, is being employed earlier as a screening tool in many patients with spine-related symptoms. Minimally invasive techniques and advances in instrumentation are improving surgical treatment. Intraoperative monitoring procedures provide improved outcomes for patients undergoing surgical resection of intraand extramedullary tumors. Stereotactic radiosurgery, usually confined to treating intracranial pathology, is now being developed to administer high-dose radiation with surgical precision to lesions within the spine. ADDITIONAL RESOURCES Albanese V, Platania N. Spinal intradural extramedullary tumors. Personal experience. J Neurosurg Sci 2002;46(1):18-24. Avanzo M, Romanelli P. Spinal radiosurgery: technology and clinical outcomes. Neurosurg Rev 2009 Jan;32(1):1-13. Bowers DC, Weprin BE. Intramedullary spinal cord tumors. Curr Treat Options Neurol 2003;5(3):207-212. Cole JS, Patchell RA. Metastatic epidural spinal cord compression. Lancet Neurol 2008 May;7(5):459-466. Review.

Conti P, Pansini G, Mouchaty H, et al. Spinal neurinomas: retrospective analysis and long-term outcome of 179 consecutively operated cases and review of the literature. Surg Neurol 2004;61(1):34-44. George R, Jeba J, Ramkumar G, et al. Interventions for the treatment of metastatic extradural spinal cord compression in adults. Cochrane Database Syst Rev. 2008 Oct 8;(4):CD006716. Gibson CJ, Parry NM, Jakowski RM, et al. Anaplastic astrocytoma in the spinal cord of an African pygmy hedgehog (Atelerix albiventris).Vet Pathol 2008 Nov;45(6):934-938. Minehan KJ, Brown PD, Scheithauer BW, et al. Prognosis and treatment of spinal cord astrocytoma. Int J Radiat Oncol Biol Phys 2008 Aug 5. This consecutive series of patients with spinal cord astrocytoma were treated at Mayo Clinic Rochester between 1962 and 2005. RESULTS: A total of 136 consecutive patients were identified. Of these 136 patients, 69 had pilocytic and 67 had infiltrative astrocytoma. The median follow-up for living patients was 8.2 years (range, 0.08-37.6), and the median survival for deceased patients was 1.15 years (range, 0.01-39.9). The extent of surgery included incisional biopsy only (59%), subtotal resection (25%), and gross total resection (16%). The results of our study have shown that histologic type is the most important prognostic variable affecting the outcome of spinal cord astrocytomas. Surgical resection was associated with shorter survival and thus remains an unproven treatment. Postoperative radiotherapy significantly improved survival for patients with infiltrative astrocytomas but not for those with pilocytic tumors. White BD, Stirling AJ, Paterson E, et al. Diagnosis and management of patients at risk of or with metastatic spinal cord compression: summary of NICE guidance. Guideline Development Group. BMJ 2008 Nov 27;337:a2538.

Anatomic Aspects of Cerebral Circulation Claudia J. Chaves

T

he brain and meninges are supplied by arteries derived from the common carotid artery (CCA) and vertebrobasilar system (Fig. 54-1). The right CCA usually originates from the brachiocephalic trunk, whereas the left CCA originates directly from the aortic arch. Both vertebral arteries (VAs) originate from the subclavian arteries. The morphologic variants of the CCA and VAs usually are not clinically significant. The CCA bifurcates at approximately the level of the sixth cervical vertebrae into the external and internal carotid arteries. The external carotid artery (ECA) supplies the neck, face, and scalp. The internal carotid artery (ICA) and its branches are mostly responsible for the arterial supply of the anterior two thirds of the cerebral hemispheres (anterior circulation). The vertebrobasilar and posterior cerebral arteries (PCAs) supply blood to the brainstem, cerebellum, occipital lobes, and posterior portions of the temporal and parietal lobes (posterior circulation).

THE CAROTID ARTERY SYSTEM External Carotid Artery At its origin, the ECA deviates anteriorly and medially in relation to the ICA in the neck and provides many branches to the neck (superior thyroid, ascending pharyngeal arteries) and face (lingual and facial arteries). As the artery ascends, occipital and posterior auricular branches supply the scalp in their named areas. The occipital artery, however, also has several meningeal branches that supply the posterior fossa and dura. Within the substance of the parotid gland, the ECA divides into its two terminal branches, the superficial temporal and maxillary arteries. The superficial temporal artery is the main supply to the scalp over the frontoparietal convexity and its underlying muscles. The more proximal branches also supply the masseter muscle. The superficial temporal artery is commonly involved in giant cell arteritis, an important consideration in the elderly with headaches, and can be palpated anterior to the tragus and in the temporal area (Chapter 11). The maxillary artery supplies the face and, through its middle meningeal branch, provides most of the blood supply to the dura mater covering the brain. The middle meningeal artery is often implicated in the formation of epidural hematomas in patients with temporal or parietal bone skull fractures (Chapter 59). The ECA occasionally has an important role in supplying collateral flow for ICA occlusive disease through anastomoses between its facial, maxillary, and superficial temporal branches and the ophthalmic artery.

Internal Carotid Artery There are four ICA segments: cervical, petrous, cavernous, and supraclinoid. The cervical segment ascends vertically in the

54  neck, posterior and slightly medial to the ECA. Significant atherosclerotic disease is usually located at the ICA origin, with potential for artery-to-artery embolism, stenosis with eventual occlusion, or both. Unlike the ECA, this segment does not have branches, allowing differentiation between the two vessels on imaging scans. The ICA enters the skull through the carotid canal within the petrous bone. This petrous segment has two small branches, the caroticotympanic and pterygoid branches, which are usually clinically irrelevant. The cavernous segment, usually called the carotid siphon because of its shape, is the portion of the ICA within the cavernous sinus and provides minor branches supplying the posterior pituitary (meningohypophyseal artery) and the abducens nerve. Of its many branches, the ophthalmic artery is the most significant. The ophthalmic artery arises from the ICA just as it pierces the dura and emerges from the cavernous sinus to pass through the optic canal into the orbit just below and lateral to the optic nerve. It supplies the globe and orbital contents through its 3 major branches: the ocular (central retinal and ciliary arteries), orbital, and extraorbital branches. The ophthalmic artery forms extensive anastomoses with branches of the ECA. The supraclinoid segment is the last portion of the ICA. It begins when this segment penetrates the dura. The posterior communicating artery (P-com) and the anterior choroidal artery are the two important branches originating at this level. The ICA then bifurcates into the anterior cerebral artery (ACA) and middle cerebral artery (MCA). The P-com is often hypoplastic. When present, it travels posteriorly to communicate with the posterior circulation at the level of the posterior cerebral artery (PCA). The P-com also provides thalamoperforate branches that supply the anteromedial thalamus and parts of the cerebral peduncles. Its presence and size is variable but often serves as an important collateral pathway in extensive cerebrovascular disease allowing flow from the anterior to the posterior circulation or vice versa. The anterior choroidal artery arises from the posterior surface of the ICA just above the P-com origin. This artery supplies an extensive cerebral area, including the visual system (optic tract, anterior portion of the lateral geniculate body and optic radiations), genu and posterior limb of the internal capsule, basal ganglia (medial globus pallidus and tail of the caudate), the diencephalon (portions of the lateral thalamus and the subthalamic nuclei), the midbrain (substantia nigra and portions of the cerebral peduncle), the medial temporal lobe (uncus, pyriform cortex, amygdala), and the choroidal plexus of the temporal horn and atrium. The ACA travels medially and anteriorly toward the interhemispheric fissure. It supplies the anterior portions of the basal ganglia and internal capsule and most of the mesial portion of the frontal and parietal lobes. The first segment of the ACA, the A1 segment, begins at the carotid bifurcation and terminates



CHAPTER 54  •  Anatomic Aspects of Cerebral Circulation  493

Left middle meningeal artery

Right and Ieft middle cerebral arteries

Right and Ieft posterior cerebral arteries

Right and Ieft anterior cerebral arteries Anterior communicating artery

Right and Ieft superior cerebellar arteries

Right ophthalmic artery Right posterior communicating artery

Basilar artery

Cavernous sinus

Mastoid branch of Ieft occipital artery Left interior auditory (labyrinthine) artery

Right deep temporal artery

Posterior meningeal branch of Ieft ascending pharyngeal artery

Right maxillary artery Right middle meningeal artery

Right and Ieft anterior inferior cerebellar arteries

Right superficial temporal artery

Right and Ieft posterior inferior cerebellar arteries Posterior meningeal branches of right and Ieft vertebral arteries Anterior meningeal branch of right vertebral artery Right posterior auricular artery Right occipital artery Right interior carotid artery Right ascending pharyngeal artery Right carotid sinus Right vertebral artery Transverse process of C6

Right exterior carotid artery Right facial artery Right lingual artery Carotid body Right superior laryngeal artery Right superior thyroid artery Thyroid cartilage Right common carotid artery Right inferior thyroid artery Right interior thoracic artery

Right deep cervical artery Right thyrocervical trunk

Brachiocephalic trunk

Right costocervical trunk Right subclavian artery

Figure 54-1  Arteries to Brain and Meninges.

at the level of the anterior communicating artery, which connects opposite A1 segments and constitutes an important collateral pathway in carotid artery occlusive disease. Occasionally, a single A1 exists supplying both medial frontal hemispheres from a single side and is termed an azygous ACA. The recurrent artery of Heubner is the most important branch of the A1 segment and supplies the anteroinferior portion of the head of the caudate, the putamen, and the anterior limb of the internal capsule. The ACA continues as the A2 segment, where the orbitofrontal branch arises and travels around the genu of the corpus callosum to the orbital and medial surface of the frontal lobe whereas the frontopolar branch supplies the rest of the medial surface of the frontal lobe. The ACA then gives off its two major branches, the pericallosal artery that runs just above the corpus callosum and the callosomarginal artery paralleling the cingulate gyrus. These two arteries supply the mesial portions of the frontal and parietal lobes. One of the major fail-safe systems within the cerebral circulation is the circle of Willis, formed by the connections between the ACAs, the anterior communicating arteries, the supraclinoid carotid, the P-coms, and PCAs. This vascular network often provides alternative conduits for perfusion avoiding the development of cerebral infarction when a major vessel becomes significantly diseased or occluded, as with cervical ICA atherosclerotic disease. The respective junctions of each

of these vessels in the Circle of Willis is the primary site of berry aneurysm formation—the major cause of subarachnoid hemorrhages. The MCA originates from the supraclinoid carotid stem and, subsequently, travels laterally to the sylvian fissure as the mainstem M1 segment, giving off lenticulostriate branches to the basal ganglia. As the MCA approaches the sylvian fissure, it usually divides into two large trunks, the superior and inferior divisions. Occasionally, the MCA trifurcates, and a middle trunk is also present. Different branches supply the frontal (orbitofrontal, ascending frontal, precentral, and central branches), parietal (anterior and posterior parietal and angular branches), and temporal (anterior and posterior temporal) lobes. The orbitofrontal, ascending frontal, precentral, and central branches usually arise from the superior division of the MCA, whereas the angular, anterior and posterior temporal branches arise from the inferior division. The anterior and posterior parietal branches can arise from either division (Fig. 54-2). The MCA stem or its distal bifurcation point are classic sites where large cerebral artery emboli lodge and are sometimes amenable to emergent intra-arterial thrombolytic therapy.

VERTEBROBASILAR ARTERIES The vertebral arteries (VAs) usually originate from the subclavian arteries on either side (see Fig. 54-1). They have 4 portions: 3

494  SECTION XII  •  Cerebrovascular Diseases

Lateral view

Central (rolandic) branch Precentral (prerolandic) branch

Anterior parietal branch Terminal cortical branches of Ieft posterior cerebral artery

Ascending frontal (candelabra) branch Terminal cortical branches of anterior cerebral arteries Lateral orbitofrontal artery

Posterior parietal branch Angular branch Posterior temporal branches

Left middle cerebral artery

Anterior temporal branches

Left anterior cerebral artery Anterior communicating artery Right anterior cerebral artery Left internal carotid artery

Medial view

Posterior Middle Anterior Callosomarginal artery

Internal frontal branches

Frontopolar artery Right anterior cerebral artery Medial orbitofrontal artery Anterior communicating artery Recurrent artery (of Heubner) Right internal carotid artery

Paracentral artery Pericallosal artery Precuneal artery Posterior pericallosal artery Parietooccipital branch Right posterior cerebral artery Calcarine branch Posterior temporal branch Anterior temporal branch Posterior communicating artery

Figure 54-2  Arteries of Brain (Lateral and Medial Views).

extracranial and one intracranial. From their origin, the VAs travel posteriorly (prevertebral segment) and enter the transverse foramen of the sixth cervical vertebrae. They then extend superiorly to exist at C2 (cervical segment), sharply turning posteriorly around the auricular process of the atlas (atlantic segment), then proceeding rostrally, piercing the posterior atlanto-occipital membrane and the dura mater to enter the intracranial cavity through the foramen magnum (intracranial or intradural segment). The vertebral arteries are prone to dissection at their entry and exit sites through the vertebra and are prone to temporal arteritis right at the dural junction. The intracranial segments course anteriorly lateral to the medulla, then ascend medially to the pontomedullary junction, where they unite at the pontine midline to from the basilar artery (Fig. 54-3). The cervical branches of the VAs give muscular, vertebral body and radicular branches and may serve as collateral conduits in cases of cervical artery compromise or occlusion. The intracranial branches are neurologically more significant and, if diseased, often give definite neurologic syndromes. The first of these are the lateral medullary branches supplying the lateral portions of the medulla. Distally the posterior–inferior cerebellar arteries (PICAs) primarily supply the posterior and inferior regions of the cerebellum but also the dorsum of the medulla oblongata. Classic Wallenberg syndrome results from occlusion of medullary arteries of the PICA or penetrator branches of the vertebral arteries.

The anterior spinal artery arises from paired medial VA branches just before the basilar junction unites in the midline to form a single vessel running the full length of the spinal cord caudally in the anteromedial sulcus. It also supplies the medial portions of the medulla; however, adequate collateral circulation in this location makes the medial medullary syndrome rare. In contrast, the anterior spinal artery within the cord is crucial to spinal cord function, and its occlusion leads to an anterior spinal artery syndrome (Chapter 45). The posterior spinal arteries arise from the PICAs or intracranial VAs and run caudally, supplying the posterior and lateral aspect of the spinal cord. The basilar artery courses rostrally on the anterior surface of the pons, and along the clivus to end at the pontomesencephalic junction providing a number of important branches on its way. The anterior–inferior cerebellar arteries (AICAs) usually arise from the midportion of the basilar artery and supply the brachium pontis, lateral pontine tegmentum, flocculus, and anteroinferior portions of the cerebellum. The internal auditory artery may arise from the AICAs or the basilar itself and supplies the vestibular and cochlear structures. The superior cerebellar arteries (SCAs) arise from the distal portion of the basilar artery before it bifurcates into the posterior cerebral arteries (PCAs). During their course around the midbrain, the SCAs provide branches to the superior lateral pontine tegmentum and the tectum of the mesencephalon. The SCAs then travel toward the cerebellum, supplying the superior vermis, lateral portion of the cerebellar hemispheres and most of the cerebellar nuclei and the cerebellar



CHAPTER 54  •  Anatomic Aspects of Cerebral Circulation  495

Medial frontobasal (orbitofrontal) artery Anterior communicating artery

Circle of Willis

Anterior cerebral artery Distal medial striate artery (recurrent artery of Heubner) Internal carotid artery Anterolateral central (lenticulostriate) arteries Middle cerebral artery Lateral frontobasal (orbitofrontal) artery Prefrontal artery Anterior choroidal artery Posterior communicating artery Posterior cerebral artery Superior cerebellar artery Basilar artery Pontine arteries Labyrinthine (internal acoustic) artery Anterior inferior cerebellar artery Vertebral artery Anterior spinal artery Posterior inferior cerebellar artery (PICA) (cut) Posterior spinal artery Distal medial striate artery (recurrent artery of Heubner) Anterior communicating artery Anterior cerebral artery Middle cerebral artery Posterior communicating artery Anterior choroidal artery Optic tract Posterior cerebral artery Cerebral crus Lateral geniculate body Posterior medial choroidal artery Posterior lateral choroidal artery Choroid plexus of lateral ventricle Medial geniculate body Pulvinar of thalamus Lateral ventricle Figure 54-3  Arteries of Brain: Inferior Views.

white matter. When the basilar artery reaches the level of the cerebral peduncles, it divides into opposite PCAs that loop laterally and posteriorly around the midbrain supplying the medial temporal lobe, portions of the parietal lobe and the occipital lobes. Perforator branches are given off to the thalamus. Distal to the posterior communicating artery, medial and lateral posterior choroidal branches off the PCA supply the posterior portion of the lateral geniculate body, optic tract, pulvinar, hippocampus, and parahippocampal gyrus, as well as the choroid plexus of the lateral and third ventricles. The basilar artery is particularly prone to atherosclerotic deposition throughout its length, and at its extremes can cause either severe stenosis or occlusion, or formation of a fusiform aneurysm by weakening the vessel wall. The rostral end of the basilar, just before bifurcating into the PCAs, is the site most likely to be occluded by an embolus leading to the classic “top of the basilar” syndrome (Chapter 55). Similarly, this is one of

the most common sites for berry aneurysms within the vertebrobasilar system.

CEREBRAL SINUSES AND VEINS Surrounded by dura, cerebral sinuses and veins are the venous structures of the brain. They typically contain inpouchings of arachnoid cells, called arachnoid granulations, which allow CSF drainage. These granulations function as one-way valves and are pressure dependent. Malfunction of these valves can occur in subarachnoid hemorrhage or meningitis, leading to normal pressure hydrocephalus. The main venous sinuses include the superior and inferior sagittal sinuses, the straight sinus, the transverse sinuses, the sigmoid sinuses, the occipital sinus, the cavernous sinuses, the superior and inferior petrosal sinuses, and the sphenoparietal sinuses. Acute or subacute cerebral venous thrombosis can be the cause of a wide range of neurologic

496  SECTION XII  •  Cerebrovascular Diseases

pathology from isolated chronic headache to venous infarction with seizures to obtundation and coma. Anatomic images and full discussion of this subject are provided in Chapter 56. The superior sagittal sinus is located within the midline of the cerebral hemispheres surrounded by dura and tethered to the inner table of the skull via the pachymeninges. It runs posteriorly from the foramen cecum to the occipitocerebellar junction. The superior sagittal sinus drains the frontal and parietal lobes through the superior cerebral veins, the largest of which is the rolandic vein in the central sulcus. This sinus often drains into the right transverse sinus. The inferior sagittal sinus parallels the corpus callosum, traveling in the inferior portion of the falx cerebri, and drains the region of the medial hemispheres and cingulate gyrus. The straight sinus is formed by the intersection of the inferior sagittal sinus and the great vein of Galen. The vein of Galen drains many smaller venous channels, including the choroidal, lateral ventricular, and thalamostriate veins and the basal vein of Rosenthal. These veins drain the choroid plexus, lateral ventricle, basal ganglia, thalamus, and medial temporal lobes. The straight sinus often drains into the left transverse sinus. The transverse sinuses lie in the grooves of the occipital bone and run laterally and forward for a short distance before diving down to become the sigmoid sinuses. Each transverse sinus receives blood from the superior petrosal sinuses, mastoid and condyloid emissary veins, inferior cerebral and cerebellar veins, and diploic veins. The sigmoid sinuses are the continuation of the

transverse sinuses and end at the jugular foramina, becoming the internal jugular veins. The cavernous sinus is an intricate venous channel interconnecting with its contralateral partner via intercavernous channels around the infundibulum. The cavernous sinus is important for the structures that it drains and for the structures that run through it. Laterally in the cavernous sinus wall are CN-III, -IV, and -V (V1 and V2 segments), and through its center runs the intracavernous portion of the ICA, the sympathetic plexus, and CN-VI. The cavernous sinuses drain into paired superior and inferior petrosal sinuses that, in turn, drain into the transverse sinus and internal jugular veins, respectively. The superior petrosal sinus connects the cavernous with the transverse sinus. It drains the tympanic cavity, cerebellum, and inferior portions of the cerebrum. The inferior petrosal sinus connects the cavernous sinus with the internal jugular vein and drains the inner ear, medulla, pons, and cerebellum. The sphenopalatine sinuses lie below the lesser wings of the sphenoid bone and drain the dura mater into the cavernous sinuses. ADDITIONAL RESOURCES Damasio, H. A computed tomographic guide to the identification of cerebrovascular territories. Arch Neurol 1983;40(3):138-142. Netter FM. The Netter Collection of Medical Illustrations. Vol 1: Nervous System. Part 1: Anatomy and Physiology. Teterboro, NJ: Icon Learning Systems; 2001. Tatu L, Moulin T, Bogousslavsky J. Arterial territories of the human brain. Neurology 1998;50:1699-1708.

Ischemic Stroke

55 

Claudia J. Chaves

I

schemic stroke is the third most frequent cause of mortality in the United States and a common cause of prolonged morbidity. Over time it has become more apparent that ischemic stroke represents a constellation of etiologies and mechanisms that often present with similar symptoms and signs. New technology has improved understanding of stroke pathophysiology that promises to translate into more specific treatments and better outcomes. The distinction between transient ischemic attacks (TIAs) and strokes based on reversibility or not of ischemic symptoms has become less clinically relevant, because a significant number of patients with transient ischemic symptoms have been found to have strokes on diffusion-weighted imaging. Therefore, the diagnostic approach to patients with transient or persistent ischemic symptoms should be the same, and treatment guided toward the underlying cause of the brain ischemia.

ETIOLOGY AND PATHOPHYSIOLOGY The most common ischemic stroke etiologies are large artery occlusive disease, cardioembolism, and small vessel disease.

Large Artery Occlusive Disease Atherosclerosis causes stenosis or occlusion of extracranial and intracranial arteries and is directly responsible for a significant percentage of cerebral ischemic events. Atheroma formation involves the progressive deposition of circulating lipids and ultimately fibrous tissue in the subintimal layer of the large and medium arteries, occurring most frequently at branching points (Fig. 55-1). Plaque formation is enhanced by bloodassociated inflammatory factors as well as increased shear injury form uncontrolled blood pressure. Intraplaque hemorrhage, subintimal necrosis with ulcer formation, and calcium deposition can cause enlargement of the atherosclerotic plaque with consequent worsening of the degree of arterial narrowing. Disruption of the endothelial surface triggers thrombus formation within the arterial lumen through activation of nearby platelets by the subendothelial matrix. When platelets become activated they release thromboxane A2, causing further platelet aggregation. The development of a fibrin network stabilizes the platelet aggregate, forming a “white thrombus.” In areas of slowed or turbulent flow within or around the plaque the thrombus develops further, enmeshing red blood cells (RBCs) in the platelet–fibrin aggregate to form a “red thrombus” (Fig. 55-2). This remains poorly organized and friable for up to 2 weeks and presents a significant risk of propagation or embolization. Either the white or red thrombus, however, can dislodge and embolize to distal arterial branches. Large artery disease can cause ischemic strokes by either intra-arterial embolism as described above and, less commonly, hemodynamic ischemia or hypoperfusion through a significantly narrowed vessel.

Frequent sites for carotid system or anterior circulation atherosclerosis are the origin of the internal carotid artery (ICA), the carotid siphon at the base of the brain (Fig. 55-3), and the main stem of the middle cerebral artery (MCA) and the anterior cerebral artery (ACA). The internal carotid artery at or around the bifurcation is usually affected in Caucasians whereas in Asian, Hispanic, and African-American populations, intracranial atherosclerosis may be more common than carotid disease. In the vertebrobasilar system, the origins of the vertebral arteries in the neck and the distal portion of the intracranial vertebral arteries are the most commonly affected areas. The basilar artery and origins of the posterior cerebral arteries (PCAs) are other sites. The main risk factors for large artery disease are arterial hypertension, diabetes, hypercholesterolemia, and smoking. Epidemiologic studies have identified hyperhomocysteinemia as a possible risk factor for atherosclerosis, with a twofold greater risk of stroke. However, recent randomized trials have not shown a correlation between moderate reduction of total homocysteine levels and vascular outcomes and theorize it may represent an “innocent bystander” rather than have a direct pathological effect. Further studies are needed to determine if there are subgroups that might benefit from a more aggressive vitamin therapy, particularly over the long term.

Cardiac Embolism Several types of cardiac disease lead to cerebral embolism: cardiac arrhythmias, ischemic heart disease, valvular disease, dilated cardiomyopathies, atrial septal abnormalities, and intracardiac tumors (Fig. 55-4). Cardiac arrhythmias including chronic or paroxysmal atrial fibrillation (AF) and sick sinus syndrome (in particular bradytachycardia syndrome) are the rhythms most associated with cardioembolic event, with stroke often being their first manifestation. Because such arrhythmias are often intermittent, careful and at times repeated monitoring is needed to identify their presence as they pose a significant risk for recurrent stroke. Within the first 4 weeks of myocardial infarction (MI), particularly with ischemia of the anterior wall, there is a higher risk of embolic stroke. More remote MIs can be a potential embolic source, particularly in patients who develop akinetic segments or left ventricular aneurysms. Mural thrombi are common in patients with dilated cardiomyopathies. Brain embolism is estimated to occur in approximately 15% of these patients. Rheumatic valvular disease, mechanical prosthetic heart valves, and infective endocarditis are well-known cardiac sources of embolism. Other relatively common abnormalities, mitral valve prolapse, mitral annulus calcification, and bicuspid aortic valve have suspected embolic potential. However, these should be considered as a potential cause of stroke only after other etiologies have been excluded.

498  SECTION XII  •  Cerebrovascular Diseases

A. Atherosclerotic plaque at arterial bifurcation

D. Thrombus formation superimposed

B. Loss of intimal continuity (ulcer formation)

E. Embolization of contents of plaque (cholesterol) and/ or platelet–fibrin; occlusion of blood vessels distally in arterial tree

C. Aggregation of platelets and fibrin on roughened surface. Platelet–fibrin emboli may occur.

F. Thrombus causes total arterial occlusion.

Figure 55-1  Atherosclerosis, Thrombosis, and Embolism.

Patent foramen ovale (PFO) and atrial septal aneurysm are risk factors for stroke. A meta-analysis of case–control studies comparing patients younger than 55 years with ischemic stroke to nonstroke controls showed an odds ratio for stroke of 3.1 for PFO alone and of 6.1 for PFO with an associated atrial septal aneurysm. Potential or presumed mechanisms of stroke included venous “paradoxical embolism,” direct embolization from thrombi formed within the PFO or atrial septal aneurysm, and thrombus from atrial arrhythmias thought to be more prevalent in this population. Atrial myxomas, although rare, are important causes of embolic strokes. These tumor emboli frequently affect the vasa vasorum, leading to the development of multiple and peripheral cerebral aneurysms similar to mycotic aneurysms.

Small Vessel Disease (Lacunes) The capillary vessel and the end penetrating arteries that supply the basal ganglia, thalamus, internal capsule, and white matter tracts are not prone to atherosclerosis as in the large-caliber cerebral circulation but undergo a characteristic pathologic degeneration in response to endothelial damage. Fibrinoid degeneration with focal enlargement of the vessel wall, foam cell invasion of the lumen, and hemorrhagic rupture through the vessel wall characterize this process known as fibrinoid degeneration or lipohyalinosis. Occlusion of these arteries causes small (1–20 mm), discrete, and often irregular lesions called

lacunes. As previously alluded to, lacunes do not involve the cortical ribbon and occur most often in the basal ganglia, thalamus, pons, internal capsule, and cerebral white matter and may cause discrete clinical syndromes but often go clinically unnoticed. Arterial hypertension and diabetes are the main risk factors (Fig. 55-5).

Arterial Dissection Dissection or tear within the extracranial ICA, particularly its pharyngeal and distal segments, or the extracranial vertebral artery, mainly in its first and third segments, are the two commonly affected vessels. Dissection occurring between the intima and media usually causes stenosis or occlusion of the affected artery, whereas dissection between the media and adventitia is associated with aneurysmal dilatation. Congenital abnormalities in the media or elastica of the arteries as seen in Marfan syndrome, fibromuscular dysplasia, and cystic medial necrosis can predispose patients to arterial dissection. Although often associated with acute trauma, arterial dissection may result from seemingly innocuous incidents, such as a fall while hiking or skiing; sports activities, particularly wrestling or diving into a wave; and paroxysms of coughing. The mechanism of stroke involves clot formation in the dissected wall of the vessel with distal propagation or embolization. Also, expansion of the clot in the dissected wall causes pro­ gressive narrowing of the lumen, leading to compromised



CHAPTER 55  •  Ischemic Stroke  499

Collagenous subendothelial tissue Platelets

Platelets circulating in blood contain thromboxane A2, a substance that promotes their aggregation, while vascular endothelium secretes prostacyclin, an aggregation inhibitor that balances this effect. These products are synthesized after conversion of arachidonic acid into intermediate endoperoxides by cyclooxygenase enzymes.

RBC RBC

If endothelial continuity is interrupted by trauma, atherosclerosis, etc., subsurface collagen is exposed to blood and stimulates adhesion of platelets to vessel wall. Platelets then discharge thromboxane A2, causing aggregation of adjacent platelets.

As more platelets aggregate, fibrin network develops and stabilizes mass into “white thrombus,” which then retracts into vascular wall. In some cases, endothelium may later heal over with or without narrowing of lumen.

If thrombus develops further, red blood cells become enmeshed in platelet-fibrin aggregate to form “red thrombus,” which may grow and block vessel lumen. Either platelet-fibrin aggregates or more fully formed clots may break off, with embolization into distal arterial branches. Figure 55-2  Role of Platelets in Arterial Thrombosis.

blood flow and hypoperfusion or, ultimately, occlusion (Fig. 55-6).

Less Common Stroke Etiologies Although frequently considered in the differential diagnosis of ischemic stroke, arteritis is a rare stroke etiology. Usually, CNS vasculitis presents as an encephalopathy with multifocal signs. Cocaine and amphetamine are the most frequent drugs associated with ischemic strokes. Vasoconstriction and vasculitis are the posited mechanisms. Hematologic disorders such as polycythemia, sickle cell disease, and thrombocytosis (usually platelets >1,000,000/dL) can cause ischemic strokes by increasing blood viscosity, hypercoagulability, or both. Antithrombin III, protein S, protein C deficiencies, factor V Leiden, and prothrombin gene mutation are usually associated with venous and not arterial thrombosis

but may take on importance in cases of stroke associated with PFO due to passage of venous clots through an intra-atrial defect (paradoxical embolization).

CLINICAL PRESENTATION Large Artery Occlusive Disease CAROTID ARTERY DISEASE

Clinical Vignette A 68-year-old white man with a history of hypercholesterolemia and 50-pack-year smoking presented with transient episodes affecting the right side of his body. During the first episode, he had weakness of his right leg, lasting for about 10 minutes. The second spell happened 1 week later and

500  SECTION XII  •  Cerebrovascular Diseases

Middle cerebral artery origin

Basilar artery

Anterior cerebral artery origin Fourth segment of vertebral artery

Siphon portion of internal carotid artery

Carotid bifurcation

First segment of vertebral artery Proximal subclavian artery

Figure 55-3  Common Sites of Cerebrovascular Atherosclerotic Occlusive Disease.

was characterized by speech difficulties, right facial drop, and right arm weakness that lasted for 2 hours. The patient came to the emergency department (ED) 3 days later. Brain magnetic resonance imaging (MRI) with diffusion-weighted imaging demonstrated two small strokes in the left frontal lobe, one in the ACA territory and the second one in the MCA distribution. Magnetic resonance angiography (MRA) of the head and neck was remarkable for a 70–80% stenosis of the left ICA, confirmed by carotid ultrasound. The patient was started on antiplatelet treatment and a statin. Smoking cessation education was provided. A right carotid artery endarterectomy was successful, with no subsequent TIAs.

Clinical Vignette A 70-year-old white man with arterial hypertension and high cholesterol presented with 1 month of recurrent 1- to 2-minute episodes of left extremities shaking that occurred only on standing. His blood pressure (BP) was 110/80 mm Hg, and neurologic examination showed a left pronator drift, but was otherwise normal. Head computed tomography (CT) showed small strokes in the arterial border zone between the right MCA and ACA and right MCA and PCA distributions. Head and neck computed tomography angiography (CTA) demonstrated a right

ICA occlusion. CT perfusion showed hypoperfusion in the right MCA territory, worse in the border zone areas. Collateral flow through the right ophthalmic, anterior communicating, and posterior communicating arteries was detected by transcranial Doppler and conventional angiogram. Patient was started on antiplatelet treatment as well as a statin drug and his antihypertensive medication dose was decreased, with a subsequent increase in the systolic BP to 140–150 mm Hg. No further episodes occurred.

The above vignettes illustrate the two mechanisms of stroke or TIA in large artery atherosclerotic disease, intra-arterial embolism (the first vignette) and hypoperfusion (the second vignette). Identification of the exact mechanism has important therapeutic implications. TIAs are common in patients with carotid artery disease and usually precede stroke onset by a few days or months. TIAs caused by intra-arterial embolism from a carotid source may not be stereotypical. TIA symptoms vary, depending on which ICA branch is involved. For example, patients can have a first episode of a transient right leg weakness and weeks later have another spell characterized by expressive aphasia, right facial droop and weakness of the right hand. This depends on the destination of the emboli. In the first example, the ACA territory is the



CHAPTER 55  •  Ischemic Stroke  501

Cardiac Sources of Cerebral Emboli Valve replacement with thrombus formation

Subacute bacterial endocarditis, vegetations

Mitral stenosis, mural and valvular thrombi

Myocardial infarction with mural thrombus

Arteriosclerotic heart disease

Ventricular aneurysm with intraluminal clot formation

Congestive heart failure, atrial fibrillation

Uncommon Cardiac Mechanisms in Stroke

Myocardiopathy with thrombi

Mitral valve prolapse with clots

Atrial myxomatous tumor emboli

Marantic emboli

Probable: patent foramen ovale transmitting venous clots

Figure 55-4  Cardiac Embolism.

destination and in the later example, the MCA territory. In contrast, hemodynamic “limb-shaking” TIAs as in the second vignette presented above are often stereotypical and posturally related and are usually seen in patients with high-grade ICA stenosis or occlusion. In this classic example of a hemodynamic ischemia, patients present with recurrent, irregular, and involuntary movements of the contralateral arm, leg, or both, usually triggered by postural changes and lasting a few minutes. These spells likely represent intermittent loss of cortical control and paralysis and differ from a focal seizure in which the movements are more regular and rhythmic and usually correlate with focal repetitive cortical hyperactivity seen on electroencephalogram. Another important clue to ICA disease is episodes of transient monocular blindness (TMB). TMB refers to the occurrence of temporary unilateral visual loss or obscuration that is classically described by careful observers as a horizontal or vertical “shade being drawn over one eye,” but most frequently as a “fog” or “blurring” in the eye, lasting 1–5 minutes. It often occurs spontaneously but at times is triggered by position

changes. Positive phenomena such as sparkles, lights, or colors evolving over minutes are more typical of migrainous phenomena and help to differentiate such benign visual changes from the more serious TMB, a frequent harbinger of cerebral infarct within the carotid artery vasculature. Rarely, with critical ipsilateral internal carotid stenosis, gradual dimming or loss of vision when exposed to bright light, such as glare of snow on a sunlit background, can be reported and is due to limited vascular flow in the face of increased retinal metabolic demand. Besides carotid atherosclerosis, other etiologies of TMB include cardiac embolism and intrinsic ophthalmic artery disease due to processes such as atherosclerosis or arteritis (see Giant cell or Temporal arteritis in Chapter 11), as well as decreased retinal perfusion from glaucoma or increased intraocular pressure. It is not uncommon that homonymous field deficits are reported by patients as monocular visual loss off to the affected side, and careful questioning as to whether each eye was checked independently and whether the visual difficulty involved the perception of a quadrant or one half of the visual world is essential.

502  SECTION XII  •  Cerebrovascular Diseases

Small (100-µm) artery within brain parenchyma showing typical pathologic changes secondary to hypertension. Vessel lumen almost completely obstructed by thickened media and enlarged to about 3 times normal size. Pink-staining fibrinoid material within walls.

Area of scan

Thrombus

Internal carotid artery

Common carotid artery

Detached intima Lacunar infarcts in base of pons interrupting some corticospinal (pyramidal) fibers. Such lesions cause mild hemiparesis.

Intimal tear allows blood flow to dissect beneath intimal layer, detaching it from arterial wall. Large dissection may occlude vessel lumen

Carotid dissection: Ultrasound of the carotid arterty with clot formed between layers of the artery (near the upper RICA label).

Figure 55-6  Arterial dissection.

Multiple bilateral lacunes and scars of healed lacunar infarcts in thalamus, putamen, globus pallidus, caudate nucleus, and internal capsule. Such infarcts produce diverse symptoms. Figure 55-5  Lacunar Infarction.

For example, patients with left occipital infarctions or transient ischemia may report right-sided vision loss, but further questioning reveals that they were unable to read the right side of street signs or a license plate and while covering the “unaffected” left eye the seemingly abnormal right eye had retained vision within the distribution of the unaffected left homonymous field (Fig. 55-7). As in the first vignette, strokes from intra-arterial embolism from ICA disease are usually cortically based. Symptoms depend on whether branches of the MCA, ACA, or both are involved. The PCA territory may rarely be affected by intra-arterial emboli from ipsilateral ICA stenosis or occlusion in patients with anomalous normal vascular variants as in a persistent fetal PCA.

Neurologic findings vary by the location of the occlusion and presence of collateral circulation (Fig. 55-8). A large MCA stroke is usually seen in patients with MCA main stem occlusion without good collateral flow, whereas deep or parasylvian strokes are the most common presentation when enough collateral flow is present over the convexities. Contralateral motor weakness involving the foot more than the thigh and shoulder, with relative sparing of the hand and face is the typical presentation of distal ACA branch occlusion. Conversely, prominent cognitive and behavioral changes associated with contralateral hemiparesis predominate in patients with proximal ACA occlusions and the involvement of the recurrent artery of Huebner (caudate and interior limb of internal capsule infarct). Hemodynamic strokes usually involve the border zone territory between ACA and MCA (anterior border zone), MCA and PCA (posterior border zone), or between deep and superficial perforators (subcortical border zone) and cause typical clinical symptoms outlined in Table 55-1. INTRACRANIAL MCA AND ACA DISEASE

Clinical Vignette A 70-year-old woman with history of diabetes mellitus and hypercholesterolemia presented to the ED reporting mild



CHAPTER 55  •  Ischemic Stroke  503

Ocular Signs of Carotid Artery Ischemia (Transient Monocular Blindness [TMB]) Other Causes of Transient Monocular Blindness

Internal carotid artery Ophthalmic artery

Erythrocyte sedimentation rate should be obtained to rule out TMB due to temporal arteritis.

Central retinal artery

ESR Covering one eye may reveal unsuspected monocular vision loss

Typical scintillating scotoma helps to diagnose TMB due to migraine.

Episodes generally transient (3-5 min). Visual fields during episode show monocular decreased vision. Left eye

Right eye

Fundus examination may reveal signs of retinal ischema, hemorrhages, and anterior ischemic optic neuritis.

Ocular Signs Due to Posterior Cerebral Artery Ischemia Temporal lobe Central vision spared

Posterior cerebral artery

Posterior cerebral artery ischemia including temporal lobe optic radiations often presents as a homonymous quadrantanopia.

Basilar artery Left eye

Right eye

Occipital lobe Central vision spared Posterior cerebral artery ischemia involving occipital lobe may present as a homonymous hemianopia, which patient may interpret as “poor vision” in eye opposite ischemic lobe.

Optic radiations Left eye

Right eye

Vertebral arteries

Figure 55-7  Ocular Signs of Large Vessel Disease.

right-sided weakness first noticed on awakening 2 days previously. The hemiparesis progressed to a right hemiplegia with dysarthria within 48 hours without change in the patient’s level of consciousness. Head CT demonstrated a stroke involving the left centrum semiovale. Head CTA showed a distal M1 segment stenosis. Patient was started on an antiplatelet treatment and a statin. Pharmacologic treatment for her diabetes was maximized. Once stable, patient was transferred to a rehabilitation facility with partial recovery of her motor deficits.

This vignette describes a classic course of subcortical infarct from poor perfusion of the lenticulostriate vessels secondary to a fixed lesion in the ipsilateral MCA. The patient’s symptoms evolved from relatively mild hemiparesis to complete paralysis within 2 days. Unlike large MCA infarctions, there was no

impairment of the patient’s level of consciousness despite the progressive nature of the neurologic deficit. In contrast, large cortical MCA lesions may also evolve over 2–4 days but due to development of cerebral edema and increased intracranial pressure, altered level of consciousness and even coma are commonly seen. Intrinsic occlusive disease of the MCA and ACA are more common in Asians, Hispanics, and African Americans than in Caucasians and are more common in women than in men. Arterial hypertension, diabetes, and smoking are the most common risk factors, with a lower incidence of high cholesterol, coronary artery disease, and peripheral vascular disease. Although TIAs can occur, they are not as common as in patients with ICA disease and usually occur over a shorter period of hours or days. When strokes occur, initial symptoms are typically noticed on awakening and often fluctuate during the day, supporting a hemodynamic mechanism.

504  SECTION XII  •  Cerebrovascular Diseases

Artery occluded

Lesion Anterior cerebral

Superior division Lenticulostriate Medial Lateral

Internal cartoid

Middle cerebral Inferior division

Entire territory

Middle cerebral artery

Infarct, surface

Infarct, coronal section

Clinical manifestations

Contralateral gaze palsy, hemiplegia, hemisensory loss, spatial neglect, hemianopsia Global aphasia (if on left side) May lead to decreased consciousness and even coma secondary to edema

Deep

Contralateral hemiplegia, hemisensory loss Transcortical motor and/or sensory aphasia (if on left side)

Parasylvian

Contralateral weakness and sensory loss of face and hand Conduction aphasia, apraxia, and Gerstmann syndrome (if on left side) Constructional dyspraxia (if on right side)

Superior division

Contralateral hemiplegia, hemisensory loss, gaze palsy, spatial neglect Broca aphasia (if on left side)

Inferior division

Contralateral hemianopsia or upper quadrantanopsia Wernicke aphasia (if on left side) Constructional dyspraxia (if on right side)

Entire territory

Incontinence Contralateral hemiplegia Abulia Transcortical motor aphasia or motor and sensory aphasia Left limb dyspraxia

Distal

Contralateral weakness of leg, hip, foot, and shoulder Sensory loss in foot Transcortical motor aphasia or motor and sensory aphasia Left limb dyspraxia

Anterior cerebral artery

Figure 55-8  Occlusion of Middle and Anterior Cerebral Arteries.

Table 55-1  Clinical Symptoms in Patients with Border Zone Strokes Stroke Location Anterior border zone Posterior border zone Subcortical border zone

Clinical Symptoms Contralateral weakness (proximal > distal limbs and sparing face), transcortical motor aphasia (left-sided infarcts), mood disturbances (right-sided infarcts) Homonymous hemianopsia, lower-quadrantanopsia, transcortical sensory aphasia (left-sided infarcts), hemineglect, and anosognosia (right-sided infarcts) Brachiofacial hemiparesis with or without sensory loss, subcortical aphasia (left-sided infarcts)

VERTEBROBASILAR DISEASE

Clinical Vignette A 76-year-old white man with a history of hypercholesterolemia and a previous myocardial infarction had acute onset of vertigo associated with vomiting and gait difficulties 2 days before presentation. On admission, he had sudden onset of slurred speech and lack of right arm

coordination. Head CT demonstrated an old right posterior– inferior cerebellar artery (PICA) stroke and a subacute left PICA stroke. Head MRI with diffusion-weighted imaging showed a new right superior cerebellar artery stroke. Head and neck CTA showed occlusion of the left vertebral artery (VA) origin, a hypoplastic right vertebral artery, and an embolus in the middistal portion of the basilar artery. He was started on a statin and on anticoagulation. Clinically, the patient improved significantly.

The vertebral arteries originate from the subclavian arteries in the neck. Stenosis or occlusion of the proximal subclavian arteries and the vertebral arteries at their origin rarely causes symptoms because of the concomitant development of adequate collateral circulation within the neck through the thyrocervical and costocervical trunks and other subclavian artery branches eventually flowing into the distal vertebral artery (see Fig. 55-3). More often, patients with subclavian and concomitant vertebralorigin stenosis have symptoms related only to upper extremity ischemia. They report pain, coolness, and weakness of the ipsilateral arm. Rarely does chronic atherosclerotic disease at the vertebral origins, even when bilateral, cause significant vertebrobasilar system flow reduction to cause symptoms. When stenosis or occlusion of the VA origin leads to TIAs or stroke,



CHAPTER 55  •  Ischemic Stroke  505

Table 55-2  Clinical Manifestations of Ischemia in the Vertebrobasilar System According to the Artery Involved* Involved Artery

Ischemic Manifestations

Vertebral or PICA penetrator arteries (Lateral medullary or Wallenberg syndrome) PICA AICA SCA _______________________________________________ PCA right

Ipsilateral limb ataxia and Horner syndrome, crossed sensory loss, vertigo, dysphagia, hoarseness Vertigo, nausea, vomiting, gait ataxia Gait and limb ataxia, dysfunction of ipsilateral CN-V, -VII, -VIII Dysarthria and limb ataxia ______________________________________________________________________________ Contralateral visual field cut and sensory loss, visual neglect, prosopagnosia (inability to recognize faces) Contralateral visual field cut and sensory loss, alexia without agraphia, anomic or transcortical sensory aphasia, impaired memory and visual agnosia Rostral brainstem–somnolence, vivid hallucinations, dreamlike behavior, and oculomotor dysfunction. Temporal + occipital regions—hemianopsia, fragments of Balint syndrome, agitated behavior, and amnestic dysfunction

Left Top of the basilar syndrome

*AICA, anterior inferior cerebellar artery; PCA, posterior cerebral artery; PICA, posterior–inferior cerebellar artery; SCA, superior cerebellar artery

intra-arterial embolism is the commonly recognized mechanism. The embolus usually lodges in the distal vertebral artery, causing a PICA stroke, or passes through, leading to a “top of the basilar syndrome” (Table 55-2). Distal intracranial VA atherosclerotic disease most often occurs at the level of the penetrators to the lateral medulla and at the take-off to the PICA. Occlusion at this site presents as a Wallenberg syndrome (lateral medullary syndrome) or cerebellar PICA stroke or both. Lateral medullary syndrome progressing into coma and herniation due to an associated large PICA cerebellar infarction is not uncommon and emphasizes the need to investigate and closely observe those with Wallenberg syndromes for unfolding signs of wider neurologic involvement. Atherosclerosis of the basilar artery most often affects its proximal and mid portions. Patients experience TIAs characterized by transient diplopia, dizziness, incoordination, and weakness affecting both sides at once or alternating between sides over minutes and even hours or days (Fig. 55-9). As in other occlusive large artery disease, some patients with severe basilar stenosis develop prominent headaches in the weeks before focal symptoms commence. The headache is thought to be from developing posterior circulation collateral flow. When stroke occurs, the most commonly affected area is the basis pons, with bilateral, often asymmetric, hemiparesis, pseudobulbar syndrome, abnormalities of eye movements (sixth nerve palsy, unilateral or bilateral internuclear ophthalmoplegia, ipsilateral conjugate gaze palsy, “one and one-half syndrome”), nystagmus, and if the reticular activating system is involved, coma (Fig. 55-10). Presence of coma or altered level of consciousness is dependent on collateral flow to the tegmentum from other vessels. If the pontine and midbrain tegmentum is spared, bilateral motor and sensory signs as well as varying degrees of ophthalmoplegia may be present without altered consciousness, such as in the “locked in” syndrome. Embolus to the distal basilar artery leads to the classic top of the basilar syndrome (Fig. 55-11). Affected areas are the rostral brainstem (penetrator branches from distal basilar artery), the thalamus (penetrators of the proximal PCAs), and the medial temporal and occipital lobes. Clinical presentation includes bilateral homonymous hemianopsias or cortical blindness,

confusion, vivid-formed visual hallucinations (peduncular hallucinations), and inability to form new memories. In contrast, emboli moving past the basilar tip cause only unilateral PCA occlusions, with isolated homonymous hemianopsias. Most PCA infarcts are either cardioembolic or from intraarterial embolism. Intrinsic PCA stenosis can occur but is rare. Clinical symptoms consist of transient episodes of hemivisual loss with, at times, associated contralateral sensory symptoms that precede the stroke onset by weeks or days. When headaches occur, they are often retro-orbital or around the brow. In addition to visual and sensory abnormalities, patients with left PCA strokes often have concurrent anomic or transcortical sensory aphasia, impaired memory, associative visual agnosia (recognition) and, when involving the posterior commissure, alexia without agraphia (inability to read with preserved writing). Patients with right PCA stroke often have associated visual neglect and prosopagnosia (difficulty in recognizing familiar faces or specific items of a recognizable group). Bilateral parieto-occipital damage (Balint syndrome) leads to inability to view a grouped visual stimulus as a whole (asimultanagnosia), loss of accurate visual fixation and ocular tracking (optic apraxia), and impaired precision pointing to a visual target (“optic ataxia”). Bilateral occipital cortex injuries produce an inability to recognize all visual stimuli, often with absent insight into the deficit (cortical blindness or Anton syndrome).

Cardioembolic Disease

Clinical Vignette A 59-year-old physician suddenly had difficulty driving; his wife noted that their car almost hit objects off to the right side. When questioned, he agreed that he was having difficulty seeing to the right. When this did not improve overnight, he was evaluated in the ED, revealing a dense right homonymous hemianopsia. Otherwise, neurologic and general physical examination were normal. Brain CT demonstrated a left occipital lobe hypodensity compatible with PCA infarction. MRI confirmed these findings, and MRA

506  SECTION XII  •  Cerebrovascular Diseases

Motor and sensory deficits in face (cranial nerves V and VII); unilateral, bilateral, or alternating (cranial nerves V and VII)

Abnormal eye movements (cranial nerves III, IV, and/or VI). Horner syndrome may be present.

Hemianopsia (bilateral occipital lesions— cortical blindness and Balint syndrome)

Vertigo, ataxia; motor and sensory deficits, which may be unilateral, or alternating

Dysphagia (cranial nerve X)

Dysphonia (cranial nerve X)

Headache, vomiting

Altered consciousness (partial or complete) may be fleeting, transient, or of long duration Figure 55-9  Ischemia in Vertebrobasilar Territory: Clinical Manifestations.

revealed a left PCA origin occlusion. A 48-hour Holter monitor demonstrated paroxysmal AF. Warfarin sodium was administered with careful monitoring. His right homonymous hemianopsia did not improve and he was told not to drive. Otherwise, he successfully compensated for this loss of vision.

Atrial fibrillation, paroxysmal or chronic, is one of the most common sources of cardiac brain embolism and accounts for up to 15–20% of all ischemic stroke. The incidence of atrial fibrillation in the population older than age 65 years is estimated at around 6%, but most patients do not experience embolic events. Risk factors that predispose to stroke or embolization from nonvalvular atrial fibrillation include age older than 75 years, hypertension, ejection fraction below 35%, and congestive heart failure. Conditions such as coronary artery disease, thyrotoxicosis, and female gender may represent other factors that play a lesser role. Multiple risk factor increase the likelihood of major stroke up to sevenfold and should be strongly considered for antithrombotic treatment. Those who present with TIA or stroke hold the highest risk or recurrence around 12% a year for the first year, then 5–6% yearly thereafter. Atrial flutter, although a more organized cardiac arrhythmia, still predisposes to emboli formation and should be approached in the same fashion as atrial fibrillation.

Strokes secondary to cardiac sources typically present with acute onset of focal neurologic deficits, such as sudden loss of hand control or drooping of the mouth, often associated with language dysfunction, if involving the dominant hemisphere, or neglect if involving the nondominant hemisphere. Cerebral emboli are most clinically apparent during the day, and patients often provide a precise time of stroke or TIA onset. Cardioembolic stroke typically occurs during the waking hours with patient activity, in contrast to intra-arterial thrombosis or artery-to-artery embolism that often occur in sleep when rheological factors may favor increased coagulation. The anterior carotid circulation receives 80% of cerebral blood flow and is four times more likely than the posterior vertebrobasilar circulation to be affected with emboli. Furthermore, a history of TIAs, strokes, or both, affecting both carotid and vertebrobasilar territories increases the suspicion of cardiac embolism. The vessels more often affected by cardiac emboli are the MCA and its branches, followed by the distal portion of the intracranial vertebral artery, distal basilar (top of the basilar syndrome), and the PCA territory. Emboli from recent MI typically are more likely to occur within the first 2 weeks of the acute event. Patients with anterior wall myocardial infarctions may develop segmental hypokinetic myocardial wall defects or even aneurysms. Such lesions provide a potential nidus for platelet aggregation with subsequent embolus formation.



CHAPTER 55  •  Ischemic Stroke  507

Basilar Artery Occlusion Posterior cerebral aa. SCA Pons Paramedian and short circumferential penetrating branches Basilar a. (occluded) AICA Medulla Vertebral aa. PICA Anterior spinal a.

Tegmentum of pons

Base of pons

Collateral circulation via superior cerebellar (SCA), anterior inferior cerebellar (AICA), and posterior inferior cerebellar (PICA) arteries may partially compensate for basilar occlusion. Basilar artery has paramedian, short circumferential and long circumferential (AICA) and (SCA) penetrating branches. Occlusion of any or several of these branches may cause pontine infarction. Occlusion of AICA or Large pontine infarction resulting in PICA may also cause pupillary and other ocular abnormalities, cerebellar infarction facial weakness, quadriplegia and coma Vestibular nuclei Cerebellar peduncles Abducens (VI) n. and nucleus Descending spinal tract and nucleus of trigeminal (V) n. Descending sympathetic fibers Facial (VII) n. and nucleus Spinothalamic tract Reticular substance Medial lemniscus Corticospinal (pyramidal) tract Small infarction in base of pons, Long circumferential a. evidenced chiefly by hemiparesis Short circumferential penetrating a.

Paramedian penetrating a. Basilar a. Figure 55-10  Basilar Artery Occlusion. Areas supplied by posterior cerebral arteries (blue) and clinical manifestations of infarction Medial thalamus and midbrain Hypersomnolence Small, nonreactive pupils Bilateral third cranial nerve palsy Behavioral alterations Hallucinosis

Internal carotid a. Middle cerebral a. Posterior communicating a. Thalamoperforating aa. to medial thalamus Thalamoperforating aa. to lateral thalamus

Lateral thalamus Hemisensory loss

Posterior cerebral a. Superior cerebellar a.

Hippocampus and medial temporal lobes Memory loss

Basilar a. and obstruction

Splenium of corpus callosum Alexia without agraphia

Anterior inferior cerebellar a.

Calcarine area Hemianopsia (or cortical blindness if both posterior cerebral arteries occluded)

Vertebral a.

Figure 55-11  Occlusion of “Top Basilar” and Posterior Cerebral Arteries.

Infective endocarditis presents with TIA or stroke in approximately 15% of cases, but eventually 30% of patients are likely to experience a major neurologic complication throughout the course of the illness. Individuals with valvular heart disease are particularly at risk for developing endocarditis after any

procedure that leads to transient bacteremia, even those as innocuous as dental cleaning, and should be treated beforehand with prophylactic antibiotics. Intravenously illicit drug use is also a major risk for infective endocarditis because of the reuse of nonsterilized needles. Endocarditis commonly presents with

508  SECTION XII  •  Cerebrovascular Diseases

systemic symptoms, such as fever, weight loss, and malaise as well as signs of a new-onset or changing cardiac murmur, petechial rash, microemboli to the nail beds (splinter hemorrhages) and conjunctiva, tender nodules or erythematous lesions in the palms and finger pads (Osler nodes and Janeway lesions), and retinal emboli with exudate (Roth spots). Microemboli affecting the brain diffusely often present as an encephalopathy rather than with focal neurologic findings and may be hard to diagnose in the setting of chronic medical illness.

Clinical Vignette A previously healthy 41-year-old woman had a right facial droop and difficulty speaking 1 day after she had made a continuous 10-hour car trip. At the ED, neurologic examination confirmed right central facial weakness and a mild mixed expressive and receptive aphasia. Cardiac examination and an electrocardiograph were normal. Brain MRI with diffusion-weighted imaging showed a small left insular stroke. Head and neck MRA results were normal. Transesophageal echocardiography (TEE) showed a patent foramen ovale (PFO), and her hypercoagulable screen was remarkable for protein S deficiency. Symptoms gradually improved, clearing completely within 72 hours.

Despite a clinically normal initial cardiac examination, the TEE confirmed a congenital intra-atrial heart defect. The symptom complex acuity was consistent with a cardioembolic source, justifying a careful heart evaluation. In patients of this age group, PFO is the most likely associated condition with embolic stroke. Patent foramen ovale and, less encountered atrial septal defects, are common and occur in up to one fourth of the population and usually do not cause cardiac symptoms. This intra-arterial connection is a remnant of the intrauterine fetal circulation that allows placental oxygenated blood to bypass the fetal unaerated lung vasculature directly to the left atrium and fetal systemic circulation. This conduit, which usually closes within a few months of birth, remains partially patent in a large proportion of the population. Any venue that predisposes to increased right-sided pulmonary and right atrial pressures (squatting, straining, lifting, coughing, etc.) would have the theoretical potential of transiently reversing the usual left-toright intra-atrial gradient, and prompt venous clots that are normally dissolved or filtered in the pulmonary circulation, to cross directly into the left atrium and subsequently the cerebral and systemic arterial circulation. Another presumed mechanism is turbulent or stagnant flow in and around the defect itself, with subsequent clot formation and propagation. PFOs are usually detected by Doppler echocardiography. After a brief delay, intravenous agitated saline or colloid injections are seen as echodense air bubbles crossing the intra-atrial septum from right to left. This is often aided by a Valsalva maneuver that transiently increases right-sided atrial pressure with respect to the left. Transesophageal echocardiography holds a higher sensitivity as compared to a transthoracic approach and is considered the test of choice. PFO has been shown to be more common in young

adults with cryptogenic stroke as compared to the general population and as compared to those with identifiable sources of stroke. Being a common finding, the presence of a PFO as a cause of paradoxical embolism in cryptogenic stroke remains however presumptive, and other situational, hematologic, and anatomic factors likely come into play that make the PFO clinically relevant. For example, a paradoxical embolism becomes more suspicious in a young patient with a prior history of deep venous thrombosis who presents with a stroke after a bout of coughing from an upper respiratory tract infection during a period of relative immobility. As illustrated in the vignette, patients at risk include those who are nonambulatory from prolonged illness or even seemingly inconsequential settings, such as during prolonged transoceanic flights or car trips where venous flow in the legs is diminished or stagnant. Those with coagulation disorders, either hereditary or acquired such as with hormone replacement therapy or pregnancy, are also at a higher risk. Studies show that the incidence of an associated hypercoagulable hematologic abnormality is higher in patients with cryptogenic stroke and PFO than the general population. Coagulation studies and a search for deep vein thrombosis should be included in the workup for all young patients with cryptogenic stroke and an associated PFO. Anatomic considerations also come into play. A PFO with an associated atrial septal aneurysm (>10 mm protrusion into either atrium) holds a much higher risk of recurrence of up to 19.2% over 4 years even when treated with antiplatelets. A large-size PFO (>1 cm) with many microbubbles crossing the intra-arterial septum, especially without the aid of a Valsalva maneuver, likely represents a high risk of recurrence.

Lacunar Small Vessel Disease

Clinical Vignette A 71-year-old woman with poorly controlled arterial hypertension developed subacute-onset, initially stuttering, left hemiparesis over 48 hours. She presented 2 weeks later when she had not fully recovered. There was no history of headache, sensory loss, visual changes, or language dysfunction. Neurologic examination demonstrated a pure motor hemiparesis, brisk right-sided muscle stretch reflexes, and a right Babinski sign. Brain MRI showed a lacuna within the right pons. MRA of the head and neck were normal. The patient was started on antiplatelet treatment and gradually improved during a 2-week stay at the rehabilitation unit, but remained with a slight tendency to circumduct the leg while walking, even 6 months later.

Lacunar strokes affecting the internal capsule, thalamus, striatum, or brainstem (see Fig. 55-5) can often be clinically distinguished from embolic disease by the tendency toward a more insidious onset, with deficits progressing or stuttering on over 2–4 days. Additionally, lacunar deficits have a relatively typical distribution; they affect the entire side of the body with motor and/or sensory symptoms without cortically based



CHAPTER 55  •  Ischemic Stroke  509

Table 55-3  Most Frequent Lacunar Syndromes and Their Locations Clinical Syndrome

Location

Pure motor stroke: weakness equally involving face, arm, and leg

Internal capsule (posterior limb) or basis pontis Lateral thalamus (posteroventral nucleus) Basis pontis or internal capsule Basis pontis

Pure sensory stroke: numbness or paresthesia equally involving face, arm, leg and usually trunk Ataxic hemiparesis: weakness and incoordination in the arm and/or leg Dysarthria—clumsy hand: facial weakness, severe dysarthria and dysphagia, slight weakness, and clumsiness of the hand Rare sensorimotor stroke: combination of pure motor/pure sensory symptoms and findings

Thalamus internal capsule

findings or visual changes. This is in contrast to middle cerebral artery cortical branch occlusions that tend to have a brachiofacial distribution often associated with other cognitive and/or visual signs. Patients experiencing lacunar strokes can present with TIA in up to 15–20% of instances. TIAs are stereotypical, and tend to cluster over 2–5 days, at times occurring frequently over a 24-hour period and in a crescendo fashion. Signs and symptoms vary according to the location of the ischemia (Table 55-3). Hypertension and diabetes are the most important risk factors, and proper treatment of these conditions is essential to prevent further strokes.

Arterial Dissection

Clinical Vignette A 42-year-old man with no vascular risk factors presented with acute-onset left-sided weakness and numbness. Symptoms were preceded by severe nonspecific right-sided neck and retro-orbital pain for 1 week after he had had a relatively inconsequential fall. Examination revealed evidence of a spastic left hemiparesis and hemineglect of the left arm more than the leg. Head CT showed a complete right MCA stroke, and CTA showed tapering of the right ICA 2 cm above the bifurcation, suggestive of arterial dissection. Patient was treated with heparin and subsequently with warfarin. Repeated CTA 6 months later showed complete recanalization of the right ICA. Warfarin was discontinued and the patient was placed on antiplatelet treatment.

Extracranial carotid artery dissection occurs predominantly in patients aged 20–50 years. The characteristic clinical presentation is unilateral neck or face pain followed a few days later by acute onset of neurologic signs. In patients with carotid dissection, pain is usually referred to the eye, temple, or forehead.

Ipsilateral Horner syndrome occurs in 40–50% of patients and is due to distension or pressure against the oculosympathetic fibers running along the internal carotid artery to the eye. Pulsatile tinnitus is common. Often, a history of minor trauma exists (violent coughing, cervical manipulation, whiplash injury, etc.) in the days preceding symptom onset. As in the preceding vignette, benign traumatic events can cause a slight intima tear in the carotid or vertebral arteries, leading to platelet fibrin aggregation with potential for developing artery-to-artery emboli. Similar to the carotid artery within the neck, the extracranial VA has a significant potential for sustaining traumatic dissection. Dissection usually occurs in the distal extracranial portion at C1–C2, also called the third segment, just before it penetrates the dura at the skull base. In those patients, pain is referred to the neck or back of the head and usually precedes the onset of neurologic signs by days and rarely weeks. TIAs are more common in ICA than on VA dissections. In ICA dissection, TIAs usually involve the ipsilateral eye and cerebral hemisphere. Symptoms of VA dissection are of dizziness, diplopia, gait unsteadiness, and dysarthria. In extracranial ICA and VA dissections, strokes usually affect the MCA and distal VA territories (PICA and lateral medullary). The mechanism of stroke relates to artery-to-artery embolization from clot accumulation and eventual rupture through the media into the vessel lumen. Also progressive true lumen narrowing with hypoperfusion occurs as does eventual occlusion, often following a flurry of successive TIA before the final stroke.

DIAGNOSTIC APPROACH For every patient evaluated with ischemic stroke or TIA, the location of the lesion and mechanism should be investigated thoroughly to better predict potential complications and to most effectively direct treatment. CT and MRI brain scanning have greatly enhanced our ability to diagnose and follow neurologic disease as well as guide treatment. Noninvasive arterial imaging with CTA and MRA have largely replaced catheter angiography in the initial evaluation of cerebrovascular disease and show great promise in advancing acute stroke care (Fig. 55-12).

Anatomic Site Although the precise anatomic location of an acute TIA or stroke can frequently be deduced by the history and neurologic examination, confirmation with an imaging study is needed and often provides more specific etiologic information that can direct potential treatment. In addition, intracerebral hemorrhages, subdural hematomas, or other structural lesions including benign and malignant tumors are occasionally found on brain CT and MRI in patients presenting with seemingly typical cerebrovascular events. Brain CT examination, with its immediate availability in most hospitals and short scanning time, is usually the initial study performed in individuals presenting with an acute focal neurologic deficit. Its sensitivity to detect the presence of a primary cerebral hemorrhage or a hemorrhagic infarct is a crucial starting point in determining the future course of action

510  SECTION XII  •  Cerebrovascular Diseases

A. 3-D reconstructed image of the

B. Reconstructed CTA images of cor-

C. Reconstructed CTA images of axial

D. Reconstructed CTA images of sagittal intercerebral vessels.

E. Reconstructed magnetic resonance angiography (MRA) composite of all proximal vessels.

F. Reconstructed magnetic resonance angiography (MRA) of the right internal carotid circulation.

G. Reconstructed magnetic resonance

H. Reconstructed magnetic resonance

Circle of Willis on computed tomography angiography (CTA).

angiography (MRA) of the right internal carotid circulation.

onal intercerebral vessels.

intercerebral vessels.

angiography (MRA) composite of all proximal vessels.

Figure 55-12  Intracranial Arterial Imaging with CT and MRI.

such as the use of thrombolytics, the need for surgical intervention, and the degree of blood pressure control. The head CT is often normal in the first few hours of an ischemic stroke. However, in some cases, the presence of an acute arterial occlusion can be detected by the presence of a localized intraluminal hyperdense signal, often seen in patients with MCA occlusion (Fig. 55-13A), even when the brain parenchyma shows no evolving processes. Head CT may also show early infarct changes characterized by sulcal effacement or loss of gray–white matter differentiation (Fig. 55-13B). Such findings have important therapeutic implications. A CT angiogram can confirm the presence of a thrombus (Fig. 55-13C) and help guide further intervention concerning intravenous or intra-arterial tissue

plasminogen activator (t-PA), anticoagulation, and management of blood pressure. Diffusion-weighted MRI is the most sensitive and specific test for acute ischemia, and abnormalities have been demonstrated as early as 1 hour after symptom onset. Combined with concomitant perfusion scanning information, the ischemic penumbra (area of brain with compromised cerebral perfusion but without established infarction) can be defined, and decision concerning the risk and feasibility of reperfusion intervention can now be made more effectively and safely. Other MRI sequences, such as FLAIR and T2-weighted imaging, can show the area of stroke, often 6–12 hours after onset of symptoms (Fig. 55-13D and E).



CHAPTER 55  •  Ischemic Stroke  511

A. Axial CT scan demonstrates increased density in distal right M1 segment (arrow); a hyperdense MCA sign.

D. Axial FLAIR image 11 hours later

demonstrates edema in the ischemic basal ganglia (arrows) where restricted diffusion was also noted.

B. Axial CT scan 2 cm higher demonstrates normal insular ribbon and imperceptible change in right basal ganglia (arrow)

C. Computed tomography angiography (CTA) shows opacification of a few branches proximal to the previously demonstrated clot and expected obstruction of distal right M1 segment (arrow)

E. MR angiography shows obstruction of distal right M1 segment similar to CTA (arrow)

Figure 55-13  Acute Ischemic Infarct with a Right Middle Cerebral Artery Clot.

Table 55-4  Comparison of Neurologic Imaging Techniques* Imaging Method

Advantages

Disadvantages

MRI/MRA

CTA/CTP

DWI and PWI demonstrate the area of stroke and the area at risk (penumbra), respectively. Images can be obtained rapidly (120 mm Hg or systolic blood pressure is >220 mm Hg. For thrombolytic-eligible patients, systolic blood pressure should be maintained below 180 mm Hg and diastolic below 105 mm Hg during and up to 24 hours after the treatment in order to prevent parenchymal hemorrhage. Intravenous beta blockers and calcium channel blockers such as labetalol and nicardipine, respectively, are first-line agents to control blood pressure levels in those patients. For patients with diastolic blood pressure higher than 140 mm Hg, sodium nitroprusside is the drug of choice. A randomized double-blind trial of IV recombinant tissue plasminogen activator (rt-PA) in patients with ischemic stroke treated within the first 3 hours of symptom onset showed a 12% absolute (32% relative) increase in the number of patients with minimal or no disability at 3 months in the rt-PA group. The benefit was present for all the different stroke subtypes analyzed. Similar benefits of early treatment with rt-PA within a 3-hour window were also shown in a subpopulation analysis of patients in the ATLANTIS (Alteplase Thrombolysis for Acute Noninterventional Therapy in Ischemic Stroke) trial.

Box 55-1  Contraindications for IV rt-PA* Strong Contraindications for IV rt-PA 1. Symptoms minor or rapidly improving 2. Other stroke or serious head trauma within the past 3 months 3. Major surgery within the past 14 days 4. Known history of intracranial hemorrhage 5. Sustained systolic BP >185 mm Hg 6. Sustained diastolic pressure >110 mm Hg 7. Symptoms suggestive of subarachnoid hemorrhage 8. Gastrointestinal or urinary tract hemorrhage within 21 days 9. Arterial puncture at noncompressible site within 7 days 10. Received heparin within 48 h and had increased PTT 11. Platelet count 1.7 *INR, international normalized ratio; PTT, partial thromboplastin time; rt-PA, recombinant tissue plasminogen activator

This treatment, since approved by the Food and Drug Administration (FDA), has become the standard of care for acute ischemic stroke, and all patients arriving to the hospital within the first 3 hours of symptom onset should be considered for IV rt-PA administration after appropriately screening for thrombolytic contraindications (Box 55-1). In contrast to studies of patients treated within the 3-hour window, most clinical trials of intravenous t-PA in unselected patients presenting after 3 hours of symptoms onset have not shown any clear benefit. However, recent studies using MRI screening criteria have shown a favorable outcome in patients with a baseline diffusion and perfusion mismatch. In theory, the region of hypoperfused but potentially viable brain around an irreversibly damaged area of tissue, may respond favorably to thrombolytic therapy beyond the typical 3-hour window provided the infarcted core is small. The EPITHET trial (Echoplanar Imaging Thrombolytic Evaluation Trial) that evaluated IV t-PA versus placebo in the 3–6-hour window in patients evaluated with advanced neuroimaging showed increased perfusion and a trend toward reduced infarct size in threatened tissue but did not translate into an across-the-board clinical benefit. The ECASS III (European Cooperative in Acute Stroke Study) IV t-PA trial, however, excluded patients at high risk of bleeding and large deficits and supports extending the thrombolytic window to 4.5 hours in patients younger than 80 years with moderate stroke severity who are not taking warfarin or other anticoagulants. Ultrasound-enhanced intravenous thrombolysis is a promising treatment, but so far remains to have a proven advantage and further study is needed regarding its safety and effectiveness. Patients with large artery occlusions and severe strokes show only a limited response to intravenous thrombolytics and



considerably higher rates of intracerebral hemorrhage. Intraarterial thrombolysis holds promise in improving the outcomes of these patients, and studies show a recanalization rate of major cerebral vessel occlusions of 50% as compared to around only 25% with intravenous therapy alone. A review of the available data on intra-arterial thrombolysis shows a possible reduction of mortality and more favorable outcomes with this type of therapy, though with an increased risk of hemorrhagic complications as compared to standard intravenous therapy, especially when higher doses of heparin are used during the angiographic procedure. Overall, although promising, there is currently no evidence that intra-arterial thrombolysis is better than intravenous treatment, and IV therapy should not be withheld from eligible patients except in the setting of a comparative trial. Intra-arterial t-PA can, however, be considered in patients who do not qualify for IV t-PA and for those with major intracranial vessel occlusion (basilar artery or mainstem MCA syndromes) outside the 3-hour window but within 6 hours. The combination of IV and IA thrombolysis has been studied and is based on the idea of uniting the advantages of both treatments: early intervention with IV thrombolysis and higher rates of recanalization with the use of intra-arterial therapy. Earlier trials show a better recanalization rate but with no improvement in clinical outcome when compared with intra-arterial treatment alone. Recent studies (Interventional Management of Stroke Study [IMS]) showed a 56% rate of recanalization in patients treated with the combination; however, similar outcomes and rate of symptomatic hemorrhage are seen as in the NINDS (National Institute for Neurological Disorders and Stroke) IV t-PA treatment group. Further studies are necessary to assess safety and efficacy of combined IA and IV thrombolysis. Mechanical clot disruption and endovascular embolectomy have been used in the acute treatment of ischemic stroke, with or without intra-arterial thrombolysis. The MERCI (Mechanical Embolus Removal in Cerebral Ischemia) device, a corkscrewlike coil that retrieves the thrombus, is approved by the FDA for clot removal in selected patients. Even though the MERCI trial showed a higher rate of recanalization, there was no evidence of better outcome at 90 days as compared with historical controls from the Prourokinase for Acute Ischemic Stroke II study (PROACT II) Study. The risk of symptomatic intracranial hemorrhage (8%) was similar to that with IV t-PA in the NINDS trial (6.4%). In patients that are ineligible for thrombolysis, treatment with heparin, low-molecular-weight heparin and aspirin may be considered. Aspirin (160 mg or 325 mg daily) is the only antiplatelet agent that has shown a small but statistically significant reduction in risk of early recurrent ischemic stroke, death and disability when given within 48 hours after ischemic stroke, regardless of the stroke subtype. Abciximab, unfractionated heparin, LMW heparins, and heparinoids have not been shown to reduce rate of stroke recurrence, mortality, or stroke-related mortality when used within the first 48 hours of stroke onset. Regarding stroke subtype, the TOAST (Trial of ORG 10172 in Acute Stroke) trial showed a possible benefit of IV danaparoid in patients with large artery disease; however, this observation requires prospective validation before it can be given any weight.

CHAPTER 55  •  Ischemic Stroke  515

Surgical Treatment Carotid endarterectomy (CEA) for prevention of ischemic stroke has been performed since the early1950s, but it was only in the 1990s that several large-scale trials were performed comparing this type of surgery against best medical treatment in patients with internal carotid artery stenosis. For the symptomatic patients, evidence from the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST) support CEA for severe (70–99%) symptomatic stenosis over best medical treatment, with a 17% absolute risk reduction and a 65% relative risk reduction of ipsilateral stroke at 2 years. CEA was not indicated for patients with stenosis less than 50%. For the symptomatic patients with stenosis between 50 and 69%, CEA is moderately useful and can be considered in selected patients. There is increasing evidence that specific plaque morphological features, such as “soft” noncalcific plaque with intraplaque hemorrhage and ulceration, increase the risk of stroke, and CEA may be a treatment option in symptomatic patients with only moderate degrees of ICA stenosis. NASCET showed that in symptomatic patients with stenosis of 50–69%, the 5-year rate of ipsilateral stroke in the surgical group was 15.7% compared to 22.2% among those treated medically. For patients with asymptomatic ICA stenosis from 60 to 99%, evidence from the Asymptomatic Carotid Atherosclerosis Study (ACAS) and Asymptomatic Carotid Surgery Trial (ACST) showed a modest benefit favoring CEA, with an absolute risk reduction at 5 years of 5.9% and 5.4%, respectively. The stroke risk reduction was more prominent in men and independent of the degree of stenosis or contralateral disease. Therefore, it is reasonable to consider CEA for asymptomatic stenosis of 60– 99% if the patient has a life expectancy of at least 5 years and if the rate of perioperative stroke or death for the institution or particular surgeon can be reliably kept to less than 3%. Carotid endarterectomy is one of the more common vascular procedures, with rates of perioperative mortality or stroke below 1% now achieved in many centers or practices (Fig. 55-14). A complication rate of less than 3–5% is thought to ensure overall patient benefit and most go home 1 or 2 days following surgery. Postoperative cranial neuropathies, cardiac complications, hyperperfusion syndrome with intracranial hemorrhages and rarely seizures can also occur but are rare.

Rehabilitation Advances in basic and clinical research have shown that the human brain is capable of significant recovery after stroke, provided appropriate rehabilitation treatment is applied at the right amount and time. Several new techniques have become available in the past decade, such as task-specific therapy, robotic-assisted rehabilitation, and constraint-induced movement therapy with ongoing studies about their short- and long-term efficacy. Task-specific therapy is specifically designed to deal with loss of particular abilities and seems to be more efficacious than traditional approaches for patients with motor deficits. Roboticassisted rehabilitation, especially for the upper extremities, has been shown to reduce even severe motor impairment in stroke patients. Constraint-induced movement therapy, where the

Internal carotid artery

Sloping cut through intima

External carotid artery

Common carotid artery Silastic tube inserted for shunt during endarterectomy. T permits clearance of air from tube.

Longitudinal incision to remove atherosclerotic obstruction at carotid bifurcation

Endarterectomy performed

Angiogram (lateral view) showing moderately severe stenosis at origin of left internal carotid artery, with ulceration indicated by protrusion of contrast medium (arrows). Such a case is suitable for endarterectomy.

Patient’s head turned to side; incision along anterior margin of sterno-cleidomastoid muscle

Vein graft or Dacron velour patch used to widen vessel if necessary. Arteriotomy closed by direct suture. Figure 55-14  Endarterectomy for Extracranial Carotid Artery Atherosclerosis.

Cerebral vessels at risk for embolic debris created by intervention at carotid level

Protection device deployed from catheter

Distal blood flow occurs through micropores in net.

Plaque fractured via balloon angioplasty creating embolic debris passing distally into protection “net”

Micromesh fabric particle “net” Wire loop Plaque

Plaque in internal carotid artery

Bag containing captured debris

Captured debris

Wire loop Catheter containing folded protection device passed beyond plaque

After balloon dilation, stent deployed across plaque bed, creating further embolic debris captured in net

Figure 55-15  Endovascular Balloon Angioplasty and Stenting.

At conclusion of procedure, the protection net containing debris created by the angioplasty is withdrawn into catheter and removed.

Catheter

Debris captured in protection net



unaffected arm is restrained while the paralyzed limb is left to perform intense exercises over 2 consecutive weeks, has shown a statistically and clinically significant improvement in motor arm function as compared with traditional therapy. Persistent benefits up to 2 years have been reported.

FUTURE DIRECTIONS Modern technology has improved the understanding of stroke and TIA pathophysiology, which will translate into a more rational therapeutic approach. Emerging therapies being evaluated for secondary prevention of atherothromboembolism include P2Y12 ADP receptor antagonists, thromboxane receptor antagonists, and thrombin receptor antagonists. The oral direct thrombin antagonist Dabigatran has recently emerged as an alternative to warfarin for atrial fibrillation with similar efficacy in stroke prevention and a decreased incidence of major bleeding complications in general. Unlike with warfarin, frequent dose adjustments and blood monitoring are not needed. Although Dabigatran promises to replace warfarin in the future, its current disadvantages include higher cost and slightly increased MI rates; also, it remains unclear how to best reverse its effects in cases of emergency. Endovascular techniques, such as angioplasty and stents (Fig. 55-15), will likely change the management approach for some patients with extracranial and intracranial disease. The recent Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) shows similar outcomes with carotid artery stenting (CAS) and CEA for the treatment of symptomatic and asymptomatic carotid stenosis (vascular event or death: 7.2% vs 6.8% at 2.5 years). However, 30-day stroke rates were significantly higher for stenting (4.1% vs 2.3%), whereas MI rates were higher for CEA (2.3% vs 1.1%). The choice of procedure therefore depends on a careful consideration of co-morbidities, individual risks, institutional experience, and patient preference. Angioplasty and stents have also been used for intracranial artery stenosis in patients who failed medical treatment, but results are mixed. Although effective in reducing recurrence of

CHAPTER 55  •  Ischemic Stroke  517

symptoms when successful, the complication rate of intracranial procedures remains high and its durability is in question. Future randomized studies are needed to determine its benefit. EVIDENCE Adams H, Adams R, Del Zoppo G, et al. Guidelines for the early management of patients with ischemic stroke. 2005 Guidelines Update. A scientific statement from the Stroke Council of the American Heart Association/ American Stroke Association. Stroke 2005;36:916-921. This article presents an update on the guidelines for the acute treatment of patients with ischemic stroke. Adams R, Albers G, Alberts MJ, et al. Update to the AHA/ASA recommendations for the prevention of stroke in patients with stroke and transient ischemic attack. Stroke 2008;39:1647-1652. Recent update of prior guidelines for stroke and TIA prevention with emphasis on antithrombotic use and statin therapy Chaturvedi S, Bruno A, Feasby T, et al. Carotid endarterectomy—An evidence-based review. Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology 2005;65:794-801. The authors provide an excellent evidence-based review of the efficacy of carotid endarterectomy for stroke prevention in asymptomatic and symptomatic patients with internal carotid artery stenosis. Goldstein LB, Adams R, Alberts MJ, et al. Primary prevention of ischemic stroke. A Guideline from the American Heart Association/American Stroke Association Stroke Council. Stroke 2006;37:1583-1633. Extensive review of the evidence on various stroke risk factors with recommendations for reduction of stroke risk Sacco RL, Adams R, Albers G, et al. Guidelines for prevention of stroke in patients with ischemic stroke or transient ischemic attacks. A statement for healthcare professionals from the American Heart Association/American Stroke Association council on stroke. Stroke 2006;37:577-617. This article presents guidelines for secondary prevention of strokes and TIAs. ADDITIONAL RESOURCE Caplan LR. Stroke: A Clinical Approach. 3rd ed. Boston, Mass: ButterworthHeinemann; 2000. This single-authored book written by a leader in the field focuses on all aspects of diagnosis and treatment of patients with stroke.

Cerebral Venous Thrombosis Gregory J. Allam

Clinical Vignette A 45-year-old man with a history of bipolar disorder and binges of alcohol abuse gradually developed global headaches that suddenly worsened over a 6-day period. He presented to the emergency room reporting excruciating headaches, especially while lying flat or after coughing. He described visual blurring and transient visual dimming while straining or getting up abruptly. He was slightly inattentive but had no focal weakness or numbness on examination. Ophthalmoscopy showed bilateral severe papilledema with peripapillary flame-shaped hemorrhages but no visual field loss. Computed tomographic (CT) scan of the brain showed hyperdensity in the sagittal sinus and the left transverse sinus. Cerebrospinal fluid (CSF) fluid analysis was normal but the opening pressure was elevated. Magnetic resonance imaging (MRI) of the brain showed no acute stroke or hemorrhage, but magnetic resonance venography (MRV) showed partial occlusion of the sagittal sinus, left transverse sinus, and the left jugular vein. He later admitted to drinking heavily and smoking just before his headaches worsened. There was no evidence of malignancy, and initial coagulation studies were normal. He was treated with warfarin and acetazolamide with no evidence of progressive visual loss and ultimately resolution of the headaches. Serial MRVs showed partial recanalization of the occluded cerebral sinuses and he was eventually taken off warfarin. He was admitted about 6 months later with recurrent episodes of shortness of breath and palpitations and was found to have multiple small pulmonary emboli and deep vein thrombosis. A repeat hypercoagulability screen revealed a lupus anticoagulant, and a newly available test showed the presence of a prothrombin gene mutation. He was advised to stay on warfarin life-long.

56 

sensory changes and mild left leg weakness. Unfortunately, he did not continue the prescribed anticoagulants and was readmitted 20 days later with pleuritic chest pain and shortness of breath. Bilateral deep vein thrombosis and a pulmonary embolism were diagnosed. An infrarenal inferior vena cava filter was inserted, and anticoagulation was resumed. The patient had a positive test result for anticardiolipin antibodies. This led to the diagnosis of an anticardiolipin antibody syndrome, confirming the need for long-term systemic anticoagulation.

W

hen venous drainage of the brain is compromised, arterial flow creates back-pressure into tissue capillaries causing capillary congestion, interstitial edema, decreased tissue perfusion, and ultimately ischemia. Eventually capillary rupture causes hematoma formation. This process of cerebral venous congestion followed by infarction (not conforming to strict arterial territories) and hemorrhage is the hallmark of cerebral sinus thrombosis. The causes of cerebral venous thrombosis vary (Box 56-1), but many relate to transient or permanent hypercoagulable states, with dehydration acting as a common precipitating event. A thorough investigation for such etiologies is crucial to directing long-term treatment and anticipating potential comorbidities. Attention should be given to signs of meningitis, such as fever, stiff neck, and rash. Examining the ears, sinuses, and face for infection or discharge may provide clues to possible septic venous thrombosis. Physical evidence or a history of head or neck trauma is important. Ocular pain, proptosis, and chemosis, often with combinations of cranial neuropathies, are significant signs that may indicate a basal skull or cavernous sinus thrombosis.

Clinical Vignette A 34-year-old man presented to the hospital after 1 week of increasing occipital headache, stiff neck, and chills. Brain CT and CSF analysis were normal; however, the patient was admitted to the hospital for worsening confusion and behavioral changes. Soon after admission, he had a generalized tonic-clonic seizure and underwent intubation. A brain MRI demonstrated bilateral frontal hemorrhagic infarctions with edema and a sagittal sinus thrombosis. Because of obtundation and signs of increased intracranial pressure (ICP), mannitol and an IV heparin infusion were started. A continuous intrasinus infusion of urokinase was given over 2 days. The thrombosis resolved, and he recovered consciousness. Eventually, the patient was discharged from the hospital on warfarin and anticonvulsants, with only minor left-sided

ANATOMY Although complex, cerebral venous system anatomy is best considered in three levels: the dural-based posterosuperior group, the dural anteroinferior or basal group, and the deep veins of the brain. The dura is formed of two layers, one abutting the inner calvarium and the other forming the outer meningeal covering. These layers separate in the midsagittal and transverse planes, forming dural venous sinuses ultimately draining into the jugular veins. A single superior sagittal sinus joins the often asymmetric but paired transverse sinus at the confluence of sinuses or torcular herophili (Fig. 56-1). The transverse sinuses run laterally from the occipital bone to the middle cerebral fossa along the tentorium cerebelli. The right is often larger and is continuous with the superior sagittal sinus whereas the left curves out



CHAPTER 56  •  Cerebral Venous Thrombosis  519

Box 56-1  Causes of Venous Sinus Thrombosis Hypercoagulable states, anticardiolipin antibody syndrome, etc. Head trauma, jugular trauma or canalization Parameningeal infection of the face, eye, ear, mastoids, or sinuses Meningitis, subdural empyema, brain abscess Hormonally related: pregnancy, postpartum period, oral contraceptives Dehydration Infiltrative malignancies Ulcerative colitis Systemic lupus erythematosus HIV infection Nephrotic syndrome Behçet disease

laterally as an extension of the single midline straight sinus. The straight sinus runs downward from near the splenium of the corpus callosum to the occipital protuberance. The sigmoid sinus curves down toward the skull base from the transverse sinus and joins the inferior petrosal sinus at the jugular foramen to form the jugular vein. The straight sinus (Figs. 56-1 through 56-4) is formed by the splayed falx layered over the cerebellar tentorium. The inferior sagittal sinus runs in the fold of the lower arch of the falx cerebri and joins the cerebral vein of Galen in the proximity of the posterior horns of the lateral ventricles to form the straight sinus. The superior and inferior sagittal sinuses provide drainage for the cerebral hemispheres. The great cerebral vein of Galen drains, through paired internal cerebral veins, the brainstem, cerebellum, posterior frontal and anterior parietal lobes, and thalamus; through the Optic (II) nerve Intercavernous (circular) sinus and pituitary gland Internal carotid artery Cavernous sinus Sphenoparietal sinus Superficial middle cerebral vein Oculomotor (III) nerve Trochlear (IV) nerve Trigeminal (V) nerve Middle meningeal vein Abducens (VI) nerve Superior petrosal sinus Petrosal vein Facial (VII) nerve and nervus intermedius Vestibulocochlear (VIII) nerve Glossopharyngeal (IX) nerve Vagus (X) nerve Jugular foramen Sigmoid sinus Accessory (XI) nerve Hypoglossal (XII) nerve Transverse sinus Great cerebral vein (of Galen) Opening of an inferior cerebral vein

Falx cerebri (cut) Superior ophthalmic vein Basilar plexus

Cavernous sinus

Tentorial artery

Superior and inferior petrosal sinuses

Tentorium cerebelli Straight sinus Falx cerebri (cut) Confluence of sinuses Superior sagittal sinus Falx cerebri Inferior sagittal sinus Great cerebral vein (of Galen) Sphenoparietal sinus Intercavernous sinus Superior petrosal sinus Straight sinus Inferior petrosal sinus Sigmoid sinus Jugular foramen Transverse sinus Confluence of sinuses Occipital sinus Figure 56-1  Dura Mater Venous Sinuses.

520  SECTION XII  •  Cerebrovascular Diseases

Longitudinal fissure Anterior cerebral veins Rostrum of corpus callosum Septum pellucidum Anterior septal vein Head of caudate nucleus Anterior terminal (caudate) vein Caudate veins Interventricular foramen (of Monro) Columns of fornix Thalamostriate vein Superior choroidal vein and choroid plexus of lateral ventricle Thalamus Tela choroidea of 3rd ventricle Direct lateral vein Posterior terminal (caudate) vein Internal cerebral veins Basal vein (of Rosenthal) Great cerebral vein (of Galen) Inferior sagittal sinus Straight sinus Tentorium cerebelli Transverse sinus Confluence of sinuses Superior sagittal sinus

Dissection from Above Uncal vein Anterior cerebral vein Superficial middle cerebral vein (draining to sphenoparietal sinus) Deep middle cerebral vein Inferiorcerebral veins

Cerebral peduncle Basal vein (of Rosenthal) Lateral geniculate body Medial geniculate body Pulvinar Splenium of corpus callosum Great cerebral vein (of Galen)

Inferior anastomotic vein (of Labbé)

Dissection from Below Figure 56-2  Deep and Subependymal Veins of Brain.

paired basal vein of Rosenthal, it drains the limbic system, hippocampus, and mesencephalon. The cavernous sinus runs posteriorly at the brain base from the sphenoid bone in the area of the superior orbital fissure to the petrous temporal bone. Cavernous sinus tributaries include cerebral veins and the ophthalmic vein. The cavernous sinus drains along the medial upper layer of the tentorium and through the superior petrosal sinus, coursing posteriorly to the transverse sinus. The cavernous sinus houses the carotid artery; the oculomotor, trochlear, and abducens nerves; and the ophthalmic division of the trigeminal nerve (Fig. 56-5). A mesh of venous sinuses around the pituitary and the anterior skull base connects the two cavernous sinuses across the midline. The

superior petrosal sinus drains the anterior brainstem and the anterior superior and inferior cerebellar hemispheres. Below the tentorium, along the skull base, the inferior petrosal sinus links the cavernous sinus to the sigmoid sinus (Fig. 56-1).

CLINICAL PRESENTATION General Aspects The neurologic presentation of cerebral venous thrombosis is protean. General features depend on the location of venous thrombosis and the abruptness of occlusion. In most patients, the earliest sign is an evolving, constant, diffuse headache that



CHAPTER 56  •  Cerebral Venous Thrombosis  521

Lateral ventricle

Sup. choroidal v. Caudate vv.

Veins on lateral wall of ventricle Veins on medial wall and floor of ventricle All other veins

Post. septal v.

Direct lateral v. Post. terminal (caudate) v. (post. part of thalamostriate v.) Int. cerebral v. Inf. sagittal sinus Int. occipital v.

Thalamostriate v. Ant. terminal (caudate) v. Genu of corpus callosum

Post. pericallosal v.

Ant. septal v.

Splenium of corpus callosum Interventricular foramen (of Monro)

Post. horn of lateral ventricle

Sup. thalamostriate vv.

Great cerebral v. (of Galen)

Interthalamic adhesion Ant. commissure 3rd ventricle

Straight sinus Medial atrial v.

Ant. cerebral v. Optic chiasm Deep middle cerebral v. Inf. thalamostriate vv.

Lateral atrial v.

Cerebellum

Basal v. (of Rosenthal) Inf. horn of lateral ventricle Post. mesencephalic v.

4th ventricle Median aperture (of Magendie)

Hippocampal and inf. ventricular vv. Cerebral aqueduct Caudate v. Ant. terminal (caudate) v.

Lateral aperture (of Luschka)

Carotid angiograms: venous phase (subependymal and superficial veins opacified) Post. terminal (caudate) v. Sup. anastomotic v. (of Trolard)

Thalamostriate v.

Sup. sagittal sinus Straight sinus

Sup. sagittal sinus Inf. sagittal sinus Superficial cortical vv. Transverse sinus Int. cerebral v. Great cerebral v. (of Galen) Straight sinus Lateral projection Frontal projection Ant. septal v. Transverse sinus Thalamostriate v. Int. jugular v. Inf. anastomotic v. (of Labbé) Sup. choroidal v. Basal v. (of Rosenthal)

Int. jugular v. Basal v. (of Rosenthal)

Int. cerebral v. Great cerebral v. (of Galen)

Figure 56-3  Subependymal Veins.

worsens with recumbency. Blurred vision from papilledema is often present but, unless persisting for weeks, rarely leads to significant or permanent visual loss. Sudden brief spells of visual obscuration can occur with abrupt positional changes and are thought to represent transiently decreased perfusion of swollen optic nerves. Slowed cognition or encephalopathy without localized brain lesions or focal neurologic signs may occur with long-standing cerebral thrombosis of gradual evolution, as seen in the first vignette presented above. In patients who have a more abrupt onset of cortical vein or superficial venous sinus thrombosis, cortically based often hemorrhagic lesions with focal neurologic signs and focal or generalized seizures develop. With involvement of the deep cerebral veins or more than two thirds of the superior sagittal sinus, obtundation followed by coma with decorticate or decerebrate posturing are presenting signs reflecting bihemispheric, bithalamic basal ganglionic, or brainstem dysfunction. Combinations

of painful cranial neuropathies with little involvement of consciousness occur with basal skull (jugular vein, cavernous, or petrosal sinus) sinus thrombosis.

Specific Clinical Presentations In superior sagittal sinus thrombosis (SSST), increased venous pressure from decreased drainage initially causes generalized headaches with paroxysms of pain occurring with any Valsalva-like maneuver, that is, coughing, sneezing, straining, lifting, or bending. Blurred vision may occur secondary to optic nerve head edema or associated exudates involving the macula. Permanent visual compromise is unusual and only happens when papilledema persists for weeks. Light-headedness, transient blindness, and tinnitus can occur with sudden head elevation from a lying or bending position, similar to pseudotumor cerebri.

522  SECTION XII  •  Cerebrovascular Diseases

L. sup. and inf. colliculi Basal v. (of Rosenthal) Post. mesencephalic v. Medial geniculate body Lateral mesencephalic v. Cut surface of left thalamus Lateral geniculate body Optic tract Inf. thalamostriate vv. Ant. cerebral v.

Left pulvinar Parts of cerebellum L lingula TU tuber Right thalamus CL central lobule P pyramid Int. cerebral vv. C culmen U uvula Splenium of corpus callosum D declive N nodule T tonsil Great cerebral v. (of Galen) F folium Inf. sagittal sinus Sup. cerebellar v. (inconstant) Sup. vermian v. Straight sinus

Optic (II) n.

C

Deep middle cerebral v.

C

CL Ant. pontomesencephalic v.

Falx cerebri Sup. sagittal sinus D

L

Trigeminal (V) n.

Intraculminate v.

TU

Preculminate v. Confluence of sinuses

P

N

Petrosal v. (draining to sup. petrosal sinus)

Tentorium cerebelli (cut) F

U

Transverse pontine v.

T

Vestibulocochlear (VIII) n. Facial (VII) v. Ant. medullary v. Vein of lateral recess of 4th ventricle Sup., middle, and inf. cerebellar peduncles 4th ventricle Ant. spinal v. Preculminate v. Great cerebral v. (of Galen) Precentral v. Post. mesencephalic v.

L. transverse sinus Inf. vermian v. Falx cerebelli (cut) and occipital sinus

Post. spinal v.

Inf. cerebellar hemispheric vv. Precentral v. L. lateral brachial v. Inf. retrotonsillar v. Sup. retrotonsillar v.

Vertebral angiograms: venous phase Sup. vermian v. Intraculminate v. Supraculminate v.

Cerebellar hemispheric vv.

Transverse sinus Sup. petrosal sinus

Straight sinus Confluence of sinuses Transverse sinus

Lateral projection Frontal projection Ant. pontomesencephalic v. Lat. mesencephalic v.

Cerebellar hemispheric vv.

Inf. vermian v. Sup. retrotonsillar v. Inf. retrotonsillar v.

Inf. vermian v. Sup. retrotonsillar v. Inf. retrotonsillar v.

Lat. mesencephalic v.

Petrosal v. Lat. brachial v. Transverse pontine v.

Figure 56-4  Veins of Posterior Cranial Fossa.

Optic chiasm Internal carotid a. Diaphragma sellae Oculomotor (III) n. Trochlear (IV) n. Pituitary gland Internal carotid a. Abducens (VI) n. Ophthalmic n. Cavernous sinus Maxillary n.

Figure 56-5  Cavernous Sinus and Its Cranial Nerves.

Intracerebral cortically based hemorrhages, common with SSST, are often associated with focal neurologic signs and seizures. Confusion, behavioral changes, somnolence, and coma may occur as thrombosis propagates within the sinus and ICP increases. These signs usually develop after the clot extends into the posterior third of the sinus. In most cases of SSSTs, one of the lateral sinuses is concomitantly involved (Fig. 56-6). Occasionally, isolated cortical vein thrombosis is seen without sagittal sinus involvement. The clinical picture is again one of headaches, focal neurologic dysfunction, and seizure, however without increased ICP or papilledema. Underlying causes are similar to sagittal sinus thrombosis, and treatment follows the same principles. Neuroimaging shows isolated, often hemorrhagic, ischemic lesions that are not confined to a cerebral artery territory.



CHAPTER 56  •  Cerebral Venous Thrombosis  523

A. CT 2 days after admis-

B. Magnetic resonance

sion showing left posterior frontal parietal patchy hemorrhage within the ischemic region.

venography (MRV) demonstrates absence of flow in posterior sagittal sinus and some cortical veins.

C. Digital angiogram,

D. Normal MRV for

venous phase confirms the MRV findings.

comparison.

Figure 56-6  Sagittal Sinus Thrombosis.

Deep cerebral vein thrombosis is present in 40% of superior sagittal sinus cases and is more likely to produce coma, pupillary abnormalities, ophthalmoplegia, and increased ICP than SSST alone. Sole or predominant deep venous system involvement mostly occurs in children but is reported in adults with presentations ranging from isolated drowsiness or obtundation to coma with bilateral posturing and ocular abnormalities. Survivors experience bilateral weakness, rigidity, dystonia or athetosis, memory loss, personality changes, and various neuropsychologic disturbances. Base of the skull sinus thrombosis has a clinical presentation of painful cranial neuropathies. Cavernous sinus thrombosis is often septic from facial, orbital, or middle ear infections with eye pain, proptosis, and chemosis as frequent features (Fig. 56-7). Varying degrees of ophthalmoplegia are present secondary to involvement of CN-III, -IV, and -VI running through the lateral portion of the cavernous sinus. The ophthalmic division of the trigeminal nerve (V1) also courses through this sinus, and forehead sensory changes are occasionally seen. Inferior petrosal sinus thrombosis, often septic, causes retro-orbital pain, trigeminal V1 sensory changes, and abducens nerve palsy (Gradenigo syndrome; CN-V, -VI). Localized thrombosis involving the internal jugular vein may be an extension of transverse or sigmoid sinus thrombosis or may result from catheterization or trauma. This often presents with CN-IX, -X, and -XI dysfunction (jugular foramen or Vernet syndrome).

DIAGNOSTIC APPROACH All patients with cerebral venous thrombosis should be examined for a hypercoagulable state. In addition to prothrombin time, partial thromboplastin time and platelet count, blood studies now commonly include protein C and S quantification, lupus anticoagulant, anticardiolipin antibodies, homocysteine levels, and DNA testing for factor V (Leiden factor) and prothrombin gene mutation. Lumbar puncture often shows an opening pressure greater than 200 mm H2O. The CSF protein is increased but the glucose content, unless there is associated meningitis, is usually normal. CSF RBCs, xanthochromia, and pleocytosis are commonly seen, especially in cases of septic sinus thrombosis and in cases associated with meningitis. Normal CSF analysis, although rare, does not exclude the diagnosis. Acutely, brain CT without contrast is obtained to assess for intracranial hemorrhage. It may reveal irregularly shaped paramedian cortical venous infarctions that do not conform to defined arterial distributions. The “empty delta sign,” where contrast partially fills the sinus, leaving an unenhanced island of clot within the occipital confluence, occurs in 50% of cases. Over the hemispheric convexities, thrombosed cortical vessels sometimes appear as hyperintense coiled or serpiginous signals. Diffuse edema and narrowed lateral ventricles may be apparent with or without hemorrhagic lesions.

524  SECTION XII  •  Cerebrovascular Diseases

Fever

Involvement of cranial nerves (III, IV, V, and VI) results in ophthalmoplegia and facial analgesia. Enlarged vein

Proptosis and chemosis

Bilateral proptosis, conjunctival chemosis, and ophthalmoplegia

Cavernous sinus thrombosis Network of valveless veins allows migration of septic thrombi from sinus or orbit sites to cavernous sinus.

Communication between cavernous sinuses results in bilateral disease

Septic thrombosis in cavernous sinus

Cerebral and dural abscesses Pituitary gland Anterior spread (Pott puffy tumor)

Oculomotor n. (III) Trochlear n. (IV) Abducens n. (VI)

Osteomyelitis

Trigeminal n. (V)

Cross section of cavernous sinus

Posterior spread (subdural abscess)

Posterior spread (epidural abscess)

Venous spread (frontal lobe abscess)

Figure 56-7  Intracranial Complications.

MRI and MRV have largely replaced angiography as standard imaging techniques to confirm cerebral sinus thrombosis (see Fig. 56-6). Cerebral angiography with a prolonged venous phase is now reserved for cases not clearly diagnosed by MRI or CT and for patients requiring intrasinus thrombolysis. Cerebral sinus thrombosis is often a clinical diagnosis based on a detailed history and corroborating physical findings. Imaging studies, however, have become crucial in the management of these patients from confirming the diagnosis to guiding treatment and to help in predicting the clinical course and outcome.

TREATMENT The management of sagittal sinus thrombosis consists of hydration, anticoagulation, and the treatment of any underlying cause. Because dehydration enhances clot propagation, early volume repletion is of utmost importance. Heparin is given to make the partial thromboplastin time double the control value. Anticoagulation is indicated despite hemorrhagic infarctions because the overall outcome is improved and intracranial hemorrhage is rarely worsened. Low-molecular-weight heparin has also been used with safety and efficacy. Close clinical follow-up and repeated brain CT scanning, however, are advised to monitor the size and location of cerebral hemorrhages throughout the course of treatment. Warfarin is given for long-term anticoagulation and is started after 24 hours of intravenous

heparin treatment or after the patient is stable. When indefinite anticoagulation is not needed, the duration of warfarin treatment remains unclear; accepted practice is 3–6 months. After the precipitating cause is resolved, it is best to confirm that headache and papilledema are controlled and that MRV shows, at least, partial recanalization of the sagittal sinus before discontinuing oral anticoagulants. Seizures occur in the acute phase in up to 30% of patients and are usually focal but can be generalized. Recurrent seizures should be treated promptly because they can cause increased intracranial pressure, clinical deterioration, and increased mortality. Up to 10% of patients may experience pulmonary embolism. This is suspected when respiratory deterioration and increased oxygen needs suddenly occur. If deterioration continues despite IV anticoagulation, many advocate a more invasive approach with in situ clot thrombolysis. A femoral venous catheter thread through the jugular vein to the transverse or sagittal sinus is used. An initial attempt at partial thrombolysis is usually followed by a continuous 12-hour intra-sinus infusion. Numerous case series have shown significant neurologic recovery with only a minor increase in bleeding complications. Monitoring hematomas remains necessary because expanding hemorrhagic infarcts may cause shift and herniation, necessitating acute treatment of increased ICP with osmotic agents or hyperventilation. Surgical evacuation of intracranial hemorrhage is rarely required. To decrease potential bleeding complications, rheolytic mechanical throm-



bectomy catheters alone or in combination with low doses of thrombolytic agents have been pursued with some success. Numerous cases of thrombolytic treatment have been described where significant clinical improvement occurred even in patients with several hemorrhagic infarcts and days of obtundation or coma.

CHAPTER 56  •  Cerebral Venous Thrombosis  525

exact mechanism is unknown but is not thought to relate to general reduction of overall CSF pressure, although many cases still demonstrate high lumbar puncture pressures after fenestration.

ADDITIONAL RESOURCES

PROGNOSIS AND LONG-TERM COMPLICATIONS With anticoagulation, about 80% of patients have good recovery with little or no residual disability. Poor outcomes correlate with rapid deterioration after admission, coma or obtundation on presentation, involvement of the deep venous system, and multiple cerebral hemorrhages, especially if present for days. Before the advent of anticoagulation, the mortality rate was 30–50%. A mortality rate of 6–10% remains in the acute phase. Aggressive treatment with intrasinus thrombolysis, especially in those with evidence of evolving venous infarctions and progressive obtundation, may improve outcomes and decrease the rate of early mortality but, to date, there are no randomized controlled studies to support its routine use. Long-term complications include focal or generalized seizures, headaches, and papilledema with visual loss, with approximately 10% rate of occurrence for each. Seizures may necessitate continued anticonvulsant therapy despite resolution of all other symptoms and sinus recanalization. Headache usually resolves with increasing recanalization and better venous drainage and often does not necessitate long-term therapy. The recurrence rate of cerebral thrombosis and other thrombotic events, such as deep vein thrombosis or pulmonary embolism, is estimated around 2–5%, with the majority of these patients likely requiring lifelong anticoagulation with warfarin. Papilledema, when present, should be followed with serial visual fields by an ophthalmologist. If not controlled, progressive visual loss (arcuate mid–peripheral field constriction and central visual loss with widening blind spot) is a danger, secondary to gradual optic nerve atrophy. Treatment of papilledema involves lumboperitoneal shunting, serial spinal taps, carbonic anhydrase inhibitors, or optic nerve fenestration into the orbit to relieve locally increased CSF pressure that otherwise would be transmitted to the optic nerve. Optic nerve fenestration is safe, has few complications, and rarely reoccludes. It is done unilaterally, with positive effects on both eyes. The

Baker MD, Opatowsky MJ, Wilson JA, et al. Rheolytic catheter and thrombolysis of dural venous sinus thrombosis: a case series. Neurosurgery 2001;48:487-494. De Bruijn SF, De Haan RJ, Stam J. Clinical features and prognostic factors of cerebral venous sinus thrombosis in a prospective series of 59 patients. For The Cerebral Venous Sinus Thrombosis Study Group. J Neurol Neurosurg Psychiatry 2001;70:105-108. DeBruijn SF, Stam J. Randomized placebo-controlled trial of anticoagulation treatment with low molecular weight heparin for cerebral sinus thrombosis. Stroke 1999;30:481-482. Of those treated with nadroparin 13% had a bad outcome compared to 21% in the placebo group. There were no new symptomatic intracranial hemorrhagic complications even though many patients in the treatment group initially presented with ICH. Einhaupl KM, Villringer A, Meister W, et al. Heparin treatment in sinus venous thrombosis. Lancet 1991;338:597-600. Randomized controlled study terminated after 20 patients because of a significant advantage in favor of heparin over placebo in angiographically proven cases of cerebral venous thrombosis. Ferro JM, Canhão P, Stam J, et al. ISCVT Investigators. Prognosis of cerebral vein and dural sinus thrombosis: results of the International Study on Cerebral Vein and Dural Sinus Thrombosis (ISCVT) Stroke 2004 Mar;35(3):664-670. Large multinational prospective observational study that shows good recovery in 79% of patients. A subgroup of men with venous hematomas, low Glasgow coma scores, deep venous involvement and malignancy tended to do worse. Ferro JM, Lopes MB, Rosas MJ, et al. Long-term prognosis of cerebral vein and dural sinus thrombosis: results of the VENOPORT study. Cerebrovasc Dis 2002;13:272-278. Haley EC, Brasmear HR, Barth JT, et al. Deep cerebral venous thrombosis: clinical, neuroradiological and neuropsychological correlates. Arch Neurol 1989;46:337-340. Horton JC, Seiff SR, Pitts LH, et al. Decompression of the optic nerve sheath for vision-threatening papilledema caused by dural sinus occlusion. Neurosurgery 1992;31:203-212. Mehraein S, Schmidtke K, Villringer A, et al. Heparin treatment in cerebral sinus and venous thrombosis: patients at risk of fatal outcome. Cerebrovasc Dis 2003;15:17-21. Preter M, Tzourio C, Ameri A, et al. Long-term prognosis in cerebral venous thrombosis: follow-up of 77 patients. Stroke 1996;27:243-246. Wasay M, Bakshi R, Kojan S, et al. Nonrandomized comparison of local urokinase thrombolysis versus systemic heparin anticoagulation for superior sagittal sinus thrombosis. Stroke 2001;32:2310-2317.

Subarachnoid Hemorrhage Clemens M. Schirmer and Carlos A. David

Clinical Vignette A 66-year-old woman suddenly experienced a terrible temporal pain radiating into her forehead. The headache was so severe that she almost lost consciousness. She became nauseated, vomited, and felt disoriented. Her family called emergency medical services and had her brought to the emergency room. There, she was noted to be arousable but sleepy and confused. She had nuchal rigidity, photophobia, but no focal motor deficit. An unenhanced head computed tomography (CT) showed subarachnoid hemorrhage centered in the right sylvian fissure but no brain parenchy­ mal abnormalities. Angiography demonstrated a ruptured middle cerebral artery aneurysm that was successfully clipped the next morning. The patient’s postoperative course was uneventful (Figs. 57-1 and 57-2).

Clinical Vignette A 44-year-old postal worker presented with severe headache and nuchal rigidity to an emergency room. Unenhanced head CT revealed a subarachnoid hemorrhage centered in the basal cisterns, and further evaluation with catheter angiography revealed a large aneurysm arising from the basilar artery tip. After consultation between the neurosurgeon and the interventional neuroradiologist, the decision to perform endovascular coil embolization was made and the procedure was carried out successfully. The patient recovered fully after a 3-week hospital stay but required a second procedure after 6 months when follow-up angiography demonstrated a reexpansion of the neck of the aneurysm (Figs. 57-3 and 57-4).

57 

AVMs and spinal neoplasms, especially myxopapillary ependymomas, can rarely lead to SAH. Despite the normal neurologic examination results and head CT in the vignette, the patient’s history was so compelling for a ruptured aneurysm or warning leak that her neurologist proceeded with the evaluation to find a large treatable berry aneurysm. Subarachnoid hemorrhage is a catastrophic neurologic event having a precipitous onset, frequently without any premonitory warning. In North America, 28,000 patients per year experience a ruptured aneurysm. Slightly more than half die shortly after rupture. Among those who survive to reach a hospital, there is an additional 20–25% chance of further ruptures within the first 2 weeks, and the overall mortality during the first month is approximately 50%. Of those patients who survive, only about 30% will have a favorable outcome. Aneurysmal SAH, although catastrophic, can often be treated successfully. When an aneurysm is identified before rupture, treatment can be curative, preventing the devastating effects of a SAH. Recognition of SAH, accurate diagnosis, and timely treatment are essential. Crucial points in the history of patients with a recent headache are the abruptness of pain onset and the severity of discomfort. Lack of abnormality on the neurologic examination does not exclude a symptomatic aneurysm, and therefore, a detailed history and careful evaluation of such patients is essential. Furthermore, a mild hemorrhage as in the first vignette, may not be observed on CT after just 24 hours. Therefore, in spite of a negative head CT, cases in which there is still a high suspicion of a ruptured aneurysm would require angiography to identify the aneurysm and avoid rebleeding with its associated 50% mortality rate.

CLINICAL PRESENTATION

S

ubarachnoid hemorrhage (SAH) refers to bleeding beneath the arachnoid coverings of the brain surface and within the contained cisterns. The incidence is about 6–8 per 100,000 in most countries in the northern hemisphere and is highest between the fifth and seventh decades of life. The multiple etiologies for SAH are classified into primary aneurysmal and spontaneous nonaneurysmal mechanisms. Ruptured intracranial aneurysm is the most preponderant cause of spontaneous SAH, accounting for up to two thirds of all cases. One study of acute SAH in more than 6300 patients demonstrated that 51% of the patients had ruptured intracranial aneurysm. Nonaneurysmal SAHs include arteriovenous malformations (AVMs), angiographically occult vascular malformations (cavernous malfor­ mation or angioma), idiopathic and iatrogenic coagulopathies, bacterial endocarditis, venous thrombosis, inflammatory processes such as granulomatous angiitis, arterial dissections, occasional tumors, hypertension, and drug abuse. In addition, pathologic processes within the spinal canal, such as spinal

The classic symptom of SAH is the “worst headache of one’s life.” Headaches associated with aneurysm rupture are frequently sudden in onset and often described as a severe thunderclap, excruciating and unbearable. The headache peaks rapidly and is frequently associated with pain extending across the head and toward the neck. The headache is usually global, with a constant viselike ache but occasionally throbbing. Unilateral aches or a retro-orbital stab-like pain, even fleetingly, raise the suspicion of a possible posterior communicating artery aneurysm. Nausea and vomiting, neck pain, and altered consciousness are often associated with the headache. Approximately 30% of patients are found to be confused and lethargic after the ictus. During the moment of rupture, one fourth of patients become comatose and up to 40% have transient loss of consciousness. Seizure-like activity may be observed. The incidence of true seizure activity in patients with SAH is estimated at 20%. Seizures in SAH are most commonly associated with middle cerebral artery (MCA) and anterior communicating artery



CHAPTER 57  •  Subarachnoid Hemorrhage  527

A

A. Axial CT exam shows subarachnoid hemorrhage lateralized to the right extending into the right sylvian fissure (arrow).

B Right-sided pterional approach depicting large bulging MCA aneurysm (arrowheads) before (A) and after (B) surgical clipping. Aneurysm has been decompressed with surgical clips at its base with preservation of the parent artery (arrowheads). Figure 57-2  Middle Cerebral Artery Aneurysm Clipping.

B. Frontal digital subtraction angiogram showing large right middle cerebral artery aneurysm (arrow).

Figure 57-1  Right Middle Cerebral Artery Aneurysm.

(ACA) aneurysmal rupture causing intracerebral hematomas. Unfortunately, many patients recall having a sentinel hemorrhage or warning leak with a fleeting but severe headache within the 2–3 weeks before the major ictus. This headache is somewhat milder and usually not associated with meningismus; it is often ignored until the catastrophic return of a major rupture. When evaluating patients with SAH or sudden severe headache, special attention should be focused on the level of consciousness, focal neurologic signs such as hemiparesis or cranial nerve palsies, and signs of meningismus (Fig. 57-5). Meningismus frequently occurs, associated with nuchal rigidity. Brudzinski’s

maneuver is an excellent means of evaluating meningismus; the examiner flexes the patient’s neck, precipitating hip flexion, knee flexion, and hamstring pain. Diplopia (due to abducens or oculomotor nerve palsies) and visual loss (chiasmal or optic nerve involvement) are caused by either cranial nerve compression from the aneurysmal dome or aneurysmal rupture and increased intracranial pressure (Fig. 57-6). Examination of the optic fundi frequently discloses retinal or preretinal hemorrhage, subhyaloid hemorrhages, and occasional papilledema. Hemorrhage into the vitreous results in Terson syndrome, with scarring and epiretinal membrane formation (macular pucker) and eventually visual loss or distortion. Terson syndrome is a frequent cause of visual loss in SAH, which often goes unnoticed until the patient regains consciousness 1–2 weeks later. It is often related with more severe subarachnoid bleeds that cause loss of consciousness and papilledema. Its association with ACA aneurysms is less clear. The long-term prognosis for vision in this situation is fairly good; however, a vitrectomy is occasionally required.

528  SECTION XII  •  Cerebrovascular Diseases

When the aneurysm ruptures and dissects into adjacent brain tissue, various focal deficits may also be found on examination.

DIFFERENTIAL DIAGNOSIS Patients presenting with a sudden apoplectic-type headache with associated meningismus or altered mental status must be considered to have an SAH until proven otherwise. However, SAH symptoms are sometimes confused with other disorders,

Unenhanced CT of the brain with SAH filling the basal cistern (arrowheads) and with early hydrocephalus (enlarged temporal horns, arrows). Figure 57-3  Basilar Artery Tip Aneurysmal Bleed.

A

including migraine headaches, hypertension, meningitis, cervical spine disorders, vertigo, and syncope. The various vascular headache syndromes remain the most common mimics. Although migraines are often characterized by the patient as sudden, a careful history reveals that they typically have a gradual onset, with progression over minutes to hours, at times, to the degree of excruciating pain often with nausea and vomiting. Many are preceded by a classic visual aura of fortification spectra or scintillating lights gradually evolving then regressing over minutes before the headache occurs. Cluster headache is another benign but severe headache syndrome with a well-defined clinical presentation. These headaches typically affect men, awakening them from sleep with a terrible unilateral periorbital and frontal pain. Cluster headaches are almost always associated with unilateral conjunctival injection, excessive lacrimation, and nasal stuffiness. They have a limited time course, usually lasting 45–60 minutes. They occur nightly in a temporal cluster for 6–8 weeks but may recur several times within a day. When this pattern is established, the diagnosis is secure. However, when the patient first experiences this headache in early midlife, a careful evaluation is indicated to exclude SAH. A therapeutic response to inhalation of 100% oxygen is diagnostic. Paroxysmal hemicrania is a related disorder with an equal sexual distribution. Its response to indomethacin is a specific therapeutic diagnostic modality. Orgasmic postcoital or exercise-induced headaches are another group of benign headaches that occur during sexual intercourse or with significant exercise. Those related to sexual activity generally occur precipitously at the peak of orgasm. These incapacitating severe headaches mimic the onset of an acute SAH and require the same full evaluation to exclude a ruptured aneurysm as other patients presenting with spontaneous sudden first-time severe headaches. Orgasmic, postcoital, or exercise-induced headaches are essentially diagnoses of exclusion.

B

Lateral view: vertebral artery angiography showing large basilar artery tip aneurysm before (A) and after (B) coiling. Figure 57-4  Basilar Artery Tip Aneurysm.



CHAPTER 57  •  Subarachnoid Hemorrhage  529

Sudden, severe, explosive headache

Transient or persistent alteration in consciousness ranging from disorientation to deep coma. Fever, sweating, vomiting and tachycardia are frequently present.

Diplopia and/or photophobia also common

Signs of meningeal irritation Kernig sign: resistance to full extension of leg at knee when hip is flexed

Less than 135°

Cerebrospinal fluid

Three successive fluid samples collected shortly after subarachnoid hemorrhage show frank blood or are orange tinged in color.

Brudzinski sign: flexion of both hips and knees when neck is passively flexed

CSF pressure elevated (150 mm)

Later, on repeat tap, all 3 samples are xanthochromic (yellow) as a result of hemoglobin release or bilirubin formation.

If blood is due to traumatic tap, fluid clears progressively in successive samples.

Figure 57-5  Clinical Manifestations of Cerebral Aneurysm Rupture.

DIAGNOSTIC APPROACH The clinical diagnosis of SAH is best confirmed with brain CT (Fig. 57-7). Its sensitivity is highest in the first 24 hours after headache onset. A mild hemorrhage may wash away within 24 hours but approximately 50% of severe SAHs are still visible on CT 1 week after the ictus, and only one third are seen after 2 weeks. CT confirms the presence of SAH and frequently highlights associated issues such as hydrocephalus, intraparenchymal hematoma, intraventricular hemorrhage, or subdural hemorrhage. Whenever the clinical suspicion of SAH exists but CT is negative, a lumbar puncture must be performed. A nontraumatic tap is crucial. When the presence of blood in the CSF does not clear between the first and fourth tubes, this is particularly suggestive of SAH (See Fig. 57-5). However, a more sensitive indicator is CSF xanthochromia, which represents lysis of erythrocytes with degradation of heme products into bilirubin

within the CSF. This frequently renders the CSF a yellowish color within 1–3 hours after an SAH, and often persists for approximately 2–3 weeks. When SAH is confirmed by CT or lumbar puncture, the cause of the hemorrhage is best evaluated with a four-vessel cerebral arteriogram. An aneurysmal source is found in 80–85% of arteriograms preformed for suspected SAH. If arteriography is negative after SAH, a repeat study should be performed approximately 10 days later. Although reliance on CT angiography rather than catheter angiography has been increasing, cerebral arteriography remains the accepted standard for evaluating patients with SAH. To ensure proper communication, predict outcomes, and guide management, a clinical grade for each SAH is needed. Several grading scales are available; the most widely used is the Hunt–Hess scale—a five-tiered description of the patient’s state and an indicator of prognosis (Table 57-1).

530  SECTION XII  •  Cerebrovascular Diseases

A. Cranial neuropathies

Abducens nerve palsy: affected eye turns medially. May be Oculomotor nerve palsy: ptosis, eye turns laterally and inferiorly, pupil dilated. first manifestation of intracavernous carotid aneurysm. Pain Common finding with cerebral aneurysms, especially carotid-posterior communabove eye or on side of face may be secondary to trigeminal icating aneurysms. (V) nerve involvement.

B. Visual field disturbances

Superior bitemporal quadrantanopia caused by Right (or left) homonymous hemianopsia caused supraclinoid carotid aneurysm compressing optic by compression of optic tract. Unilateral amauchiasm from below rosis may occur if optic (II) nerve is compressed.

Inferior bitemporal quadrantanopia caused by compression of optic chiasm from above

C. Retinal changes

Optic atrophy may develop as result of pressure on optic (II) nerve from a supraclinoid carotid, ophthalmic, or anterior cerebral aneurysm.

Papilledema may be caused by increased intracranial pressure secondary to rupture of cerebral aneurysm.

Hemorrhage into optic (II) nerve sheath after rupture of aneurysm may result in subhyaloid hemorrhage, with blood around disc.

Figure 57-6  Ophthalmologic Manifestations of Cerebral Aneurysms.

PATHOPHYSIOLOGY Intracranial Aneurysms Subtypes of intracranial aneurysms include saccular or berry, fusiform, dissecting, traumatic, and infectious (mycotic) aneurysms. Frequently associated with an SAH, saccular aneurysms are by far the most common type. They are spherical in shape but frequently have asymmetric outpouching and multilobulated characteristics that are felt to be potential rupture sites for the aneurysm. The aneurysmal fundus or body is connected to the parent vessel via a small neck region, and as the aneurysm grows, this neck region may broaden and incorporate normal branching vessels. Intracranial aneurysms characteristically occur at branch points of major cerebral arteries. Almost 85% of aneurysms are found in the anterior circulation and 15% within the posterior circulation (Fig. 57-8). Overall, the most common sites are the

anterior communicating artery followed by the posterior communicating artery and the middle cerebral artery bifurcation. Within the posterior circulation, the most preponderant site is at the top of the basilar artery bifurcation into the posterior cerebral arteries. Aneurysms are frequently classified according to size, with small being less than 10 mm, large 10–25 mm, and giant aneurysms larger than 25 mm. At presentation, most aneurysms are small, with only 2% found to be giant. Giant aneurysms are more likely to cause compressive symptoms on the optic chiasm, cranial nerves, and brainstem depending on location. Rarely involvement of tributary vessels, either due to aneurysmal expansion or cavitary clot, may lead to ischemic symptoms as well (Fig. 57-9). Although controversy remains regarding the association of size and the incidence of rupture, 7 mm seems to be the minimal size at the time of rupture. Overall, ruptured aneurysms tend to be larger than unruptured aneurysms.



CHAPTER 57  •  Subarachnoid Hemorrhage  531

identified, and aneurysmal SAH is equally distributed in sleep, routine daily activities, and strenuous activity. Nearly 50% of patients who have an SAH, when properly questioned, relate a history of a warning leak with headache or symptoms around 2–3 weeks before the major hemorrhage. Nearly half of these individuals die before arriving to the hospital. Many of the initial survivors succumb to a recurrent hemorrhage after presenting to the hospital. The peak incidence of subsequent hemorrhage occurs in the first 24 hours, but the subsequent daily risk continues such that approximately 20– 25% have rebled within the first 2 weeks of presentation. Mortality associated with the second hemorrhage is nearly 70%. RISK FACTORS

Unenhanced axial CT of the brain with SAH centered in the right sylvian fissure Figure 57-7  Subarachnoid Hemorrhage.

Table 57-1  Hunt–Hess Grading Scale for Berry Aneurysms Grade

Description

1

Asymptomatic, or mild headache and slight nuchal rigidity Moderate to severe headache, nuchal rigidity, no neurologic deficits other than cranial nerve palsies. Mild focal deficit, lethargy, confusion Stupor, hemiparesis, central neurologic signs Deep coma, decerebrate rigidity, moribund appearance

2

3 4 5

Aneurysms occur in approximately 5% of the adult population, somewhat more commonly in women. The causes of intracranial aneurysm formation and rupture are not well understood; however, it is thought that intracranial aneurysms form over a relatively short period and either rupture or undergo changes resulting in a stable unruptured aneurysm. Pathologic examination of ruptured aneurysms obtained at autopsy demonstrates disorganization of normal vascular architecture with loss of the internal elastic lamina, and reduced collagen content. In contrast, unruptured aneurysms have nearly twice the collagen content of the normal arterial wall, resulting in increased thickness of the aneurysmal dome, which may be responsible for the observed relative stability and low rupture rate.

Risk factors associated with aneurysmal rupture include cigarette smoking, oral contraceptive use, alcohol consumption, pregnancy, and childbirth. Possible diurnal blood pressure variations are associated with a circadian rhythm for aneurysm rupture. Most ruptures occur early in the morning or evening, but few occur in the middle of the night. There also may be a predisposition to occur during the winter months or when there are drastic changes in barometric pressure. The most likely cause of rupture is hemodynamic stress associated with biomechanical and structural weakness within the blood vessel and aneurysmal wall.

Perimesencephalic Subarachnoid Hemorrhage Of patients presenting with spontaneous SAH, approximately 15–20% have negative arteriograms. Repeated arteriography may discern another 7% of patients. However, a specific subset of individuals displays SAH with a specific CT distribution of blood over the anterior aspect of the brainstem or perimesencephalic regions. Benign perimesencephalic SAH typically occurs in nonhypertensive younger males who generally do well. Although the clinical presentation is similar to that of an aneurysmal SAH, symptom onset is more gradual and patients appear less ill. When these patients have a typical presentation and characteristic CT findings and a good-quality angiogram that is negative, a follow-up arteriogram is not always needed. The cause of benign perimesencephalic SAH is unknown but is postulated to be caused by rupture of bridging vessels across the perimesencephalic cistern.

MANAGEMENT Complications of the Ruptured Aneurysm Specific therapeutic issues pertain to ruptured aneurysms and SAH; primarily the prevention of rebleeding, management of increased intracranial pressure (ICP) and hydrocephalus, and the treatment of potential cerebral vasospasm. Associated medical sequelae lead to other management issues noted below.

RUPTURED ANEURYSMS

The peak incidence of aneurysmal SAH is in the sixth decade of life. Only 20% of aneurysm ruptures occur in patients aged between 15 and 45 years. No predisposing activity has been

REBLEEDING

Rebleeding is the major cause of poor outcome after SAH. A second hemorrhage is associated with 70% mortality rate. If

532  SECTION XII  •  Cerebrovascular Diseases

Distribution of Congenital Cerebral Aneurysms Anterior cerebral 30% Distal anterior cerebral 5% Anterior communicating 25% Internal carotid 30% Ophthalmic 4% Posterior communicating 18% Bifurcation 4% Anterior choroidal 4%

Anterior circulation 85%

Middle cerebral 25% Posterior cerebral 2% (Posterior communicating and distal posterior cerebral) Basiliar 10% Bifurcation 7%

Posterior circulation 15%

Basilar trunk 3% Vertebral—posterior inferior cerebellar 3%

Figure 57-8  Typical Sites of Cerebral Aneurysms.

Internal carotid a.

B. Aneurysm of supraclinoid

Cavernous sinus

segment of internal carotid artery elevating optic chiasm, distorting infundibulum and compressing oculomotor (III) nerve

Oculomotor (III) n. (divided) Trochlear (IV) n. Trigeminal (V) n. Abducens (VI) n. Oculomotor (III) n. (divided) Posterior communicating a. Posterior cerebral a. Basilar a.

A. Intracavernous (infraclinoid) internal carotid aneurysm compressing

abducens (VI) nerve. Oculomotor (III), trochlear (IV), and trigeminal (V) nerves may also be affected. Trigeminal involvement may cause facial pain. III IV

C. Aneurysm of basilar bifur-

cation projecting posteriorly, invading peduncles and compressing cerebral aqueduct. Corticospinal tracts may be affected, resulting in paralysis or paresis.

Figure 57-9  Giant Cerebral Aneurysms.

D. Aneurysm of middle

cerebral artery

E. Aneurysm of anterior cerebralanterior communicating arteries

F. Aneurysm of posterior inferior cerebellar artery



untreated, the risk of subsequent aneurysm rupture is approximately 4% in the first 24 hours and 1.5% per subsequent day, leading to approximately 27% incidence of subsequent aneurysmal rupture within the first 2 weeks of hemorrhage. The rebleeding rate decreases to 3–5% per year. The major goal in SAH treatment is to prevent rebleeding, ideally by methods designed to obliterate the aneurysm. Although the rebleeding risk can be somewhat decreased pharmacologically in the short term, the only definitive prevention is direct obliteration using surgical or endovascular techniques. Previous beliefs regarding the timing of aneurysm occlusion have been replaced by a general attitude that early and expeditious aneurysm occlusion, when feasible, must be performed. HYDROCEPHALUS

Up to 25% of patients with SAH develop secondary acute hydrocephalus, independent of grade that worsens if left untreated. There is no consensus on the management of hydrocephalus and intraventricular hemorrhage. However, external ventricular drainage is recommended in conjunction with early aneurysm occlusion. Many patients can be weaned off the ventricular drainage later in their hospital course. Chronic hydrocephalus develops in 25% of patients who survive aneurysmal rupture. Of patients with acute hydrocephalus who require ventricular drainage, approximately one half will ultimately require a ventricular–peritoneal shunt. CEREBRAL VASOSPASM

Cerebral vasospasm, a poorly understood phenomenon, is the most feared and difficult issue associated with SAH. This represents a pathologic change within the cerebral vessels leading to vascular narrowing with decreased cerebral blood flow and subsequent stroke. Vasospasm is correlated with poor clinical grade and larger degrees of hemorrhage. It is thought that vessel spasm and narrowing is the result of RBC degradation and lysis within the subarachnoid space with resultant imbalance between vascular relaxing and constricting factors in CSF. Typically, vasospasm develops about the fourth day after SAH and usually peaks between 7 and 10 days but may occur up to 3 weeks following bleeding. Management includes the use of calcium channel blockers such as nimodipine, decreasing ICP with ventricular drainage, and augmenting cerebral circulation and perfusion through narrowed vessels. The latter is best achieved with triple-H therapy, consisting of hypervolemia, hemodilution, and hypertensive therapy. Hypervolemia is easily achieved using volume expanders, such as albumen and crystalloid fluids. Hemodilution frequently occurs passively or with phlebotomy with an optimum hematocrit goal between 30% and 33%. Hypertensive therapy, when needed, may be instituted using α-adrenergic agonists such as phenylephrine hydrochloride. The goal is to prevent the development of permanent neurologic deficits by reversing deficits as they occur. Transcranial Doppler ultrasonography is of value for detecting the presence and degree of vasospasm and for monitoring its response to therapy. Transcranial Doppler ultrasonography provides real-time information regarding blood flow velocities, which correlates with the degree of vessel spasm.

CHAPTER 57  •  Subarachnoid Hemorrhage  533

Occasionally, ischemic deficits continue to develop despite aggressive triple-H therapy. In this setting, endovascular maneuvers, such as intracranial angioplasty, intraarterial papaverine (a direct smooth muscle relaxant) or, more recently, intraarterial calcium channel blakers such as verapamil, can be used with excellent, albeit transient, results. The voltage-gated calcium channel blocker nimodipine has been shown to decrease rates of infarctions related to vasospasm by about a third in patients with no neurologic deficits on presentation. There is no evidence that it reduces the frequency of medium or large vessel vasospasm directly, and its effect may be through enhancing cerebral blood flow through increasing microvascular and collateral flow. Its use in critically ill patients must be weighed against its potential effects of excessively lowering the blood pressure and the difficulty of administration (60 mg PO qid for 3 weeks). SYSTEMIC COMPLICATIONS

Subarachnoid hemorrhage concomitantly results in a catastrophic assault on the entire physiologic system, and patients are frequently critically ill, requiring a multisystem therapeutic approach. At the moment of SAH, experimental evidence suggests that a massive surge in ICP overcomes MAP, resulting in a momentary global arrest in cerebral circulation. As the increased ICP begins to wane, the circulation is reinstated, at which point a small fibrin plug is created, sealing the aneurysm and preventing further bleeding. The sudden ICP increase affects the hypothalamus and when combined with the associated global ischemia, there is a massive neuroendocrine response to a catecholamine surge consequently leading to possible cardiac and pulmonary injury. Cardiac abnormalities may be identified on ECG in up to 50% of patients at admission, including T-wave abnormalities, ST-segment depressions, prominent U waves, or prolongation of the QT interval. Cardiac arrhythmias and myocardial injury may develop. Other patients may present with acute respiratory distress syndrome from massive pulmonary edema, termed neurogenic pulmonary edema. It may result in associated hypoxia and may contribute to the overall system failure. There is usually associated acute hypertension, likely as part of the Cushing response, secondary to increased ICP. This reflexive mechanism is protective as it maintains mean arterial pressure and cerebral circulation in the face of a dramatic increase in ICP. Management of hypertension in this setting requires treatment of the increased ICP, such as ventricular drainage of the CSF, rather than the use of antihypertensive medications and an abrupt drop in blood pressure. Frequently, abnormalities of electrolytes are also noted, particularly hyponatremia. Usually associated with a salt wasting state rather than a syndrome of inappropriate antidiuretic hormone, hyponatremia should be managed accordingly. The mechanism is not totally clear but likely involves increased renal natriuresis as a result of heightened sympathetic tone and the release of cerebral natriuretic peptide. Unlike SIADH, the urine volume remains high and treatment entails both intravascular fluid and sodium replacement, at times with hypertonic fluids. Mineralocorticoids have also been reported to be useful.

534  SECTION XII  •  Cerebrovascular Diseases

Unruptured Aneurysms The diagnosis of an unruptured intracranial aneurysm is frequently approached with anxiety and an urge for expeditious treatment considering the high morbidity and mortality associated with SAH. However, increasing evidence suggests a basic pathophysiologic difference between unruptured and ruptured aneurysms; the risk of SAH from smaller unruptured aneurysms is likely small. The natural history of unruptured aneurysms is not completely understood. They may be classified into asymptomatic or symptomatic unruptured aneurysms. Symptomatic unruptured aneurysms often require treatment because the presenting symptom frequently is the harbinger of an oncoming bleeding episode. Various symptoms can be described, most from compression of neural structures by large or giant aneurysms: cranial nerve deficits, especially of CN-III, headaches, eye pain, as well as hemiparesis or motor deficits. Some aneurysms develop intraaneurysmal thrombosis that may lead to thromboembolic stroke or transient ischemic attacks. The number of unruptured aneurysms receiving medical attention has increased significantly with the advent of imaging studies such as CT angiography and MRA. Traditionally, patients with unruptured aneurysms were thought to have a high risk of bleeding and were therefore considered for obliteration therapies. However, the International Study of Unruptured Intracranial Aneurysms raised concerns about treating all unruptured aneurysms. Despite criticisms regarding this report, conventional thinking and management of truly asymptomatic unruptured aneurysms is being reexamined. Truly asymptomatic unruptured aneurysms are less prone to bleeding than symptomatic unruptured aneurysms. These lesions are frequently discovered during investigation of other neurologic complaints or screening of high-risk patients, such as those with a familial history of aneurysms, connective tissue disorders, or polycystic kidney disease. Their natural history has been the focus of much controversy, mainly stemming from the International Study of Unruptured Intracranial Aneurysms. An initially suggested hemorrhage risk of approximately 0.05% per year in patients with aneurysms smaller than 10 mm has been supplanted by further analysis demonstrating a low risk associated with aneurysms smaller than 7 mm. It is recommended that aneurysms larger than 7 mm should be treated. Aneurysms smaller than 7 mm should be considered for treatment in patients with a familial history of SAH, patients who have had SAH associated with a separate aneurysm, and very young patients for whom the lifetime risk may become significant.

Saccular Aneurysms The obliteration and elimination of saccular aneurysms from the circulation has undergone a revolutionary change. Less invasive endovascular routes have provided an attractive alter­native, particularly in elderly and high-risk patients, to traditional treatment with surgical clipping of the aneurysm via craniotomy. Despite the enthusiasm for endovascular approaches, studies suggest a 20–30% recurrence rate. Furthermore, this treatment frequently results in less than 100% obliteration of the aneurysm. The remaining unanswered question is whether the 1–2%

remnants of aneurysms frequently associated with endovascular coil obliteration pose a risk of subsequent SAH. In contrast, aneurysmal surgical clipping has withstood the test of time. With successful neurosurgical clipping, the recurrence risk is less than 1%. However, the risks of surgical aneurysm clipping are slightly higher than those with endovascular obliteration, particularly with aneurysms of the posterior circulation.

Technical Aspects of Surgical Clipping Craniotomy and aneurysm obliteration by clipping is the most effective treatment available. Aneurysms completely obliterated using this technique almost never recur. Overall, surgical treatment of unruptured aneurysms is associated with 3% mortality and 7% morbidity. The following discussion illustrates lesions’ anatomical complexities and unique features. The development of the surgical microscope and micro­ surgical instrumentation and the evolution of skull base techniques have revolutionized treatment of cerebral aneurysms. Magnification and brilliant illumination of very narrow exposure windows have allowed the preservation of small perforating vessels that are not easily visible to the naked eye and serve as strategic end arteries of eloquent brain regions. The advent of skull base techniques in which bone is removed to obviate any brain retraction and manipulation has also facilitated the treatment of aneurysms, particularly the more complex and giant variety. CRANIOTOMY

Different approaches are used depending on the location, size, and shape of the aneurysm. Most anterior circulation aneurysms are done via a pterional craniotomy, a fundamental approach in aneurysm surgery. As its name implies, it centers on the pterion and encompasses both the frontal and temporal bone removal to expose the sphenoid wing. After the dura is opened, the frontal and temporal lobes are seen in the region of the sylvian fissure. The surgical microscope is brought into the field to accomplish the remaining surgery with magnified vision (Fig. 57-10). Posterior circulation aneurysms can be approached posteriorly (Fig. 57-11), via a pterional-transsylvian route or subtemporal route, depending on the projection and height of the basilar bifurcation. Other more complex approaches such as orbito-zygomatic skull base approaches and far-lateral appro­ aches can also be employed for posterior circulation aneurysms as needed. A detailed discussion of surgical approaches is beyond the scope of this chapter. INTRACRANIAL SURGICAL DISSECTION

The neurosurgeon proceeds through the natural arachnoidal and cisternal compartments to expose the appropriate vessels and the parent artery. Dissection of the aneurysm, particularly its neck, as well as all branches and perforating vessels is completed before an appropriate aneurysm clip is placed across the aneurysm neck, sealing it from the parent vessel circulation. Close inspection to ensure that no perforating branch arteries



CHAPTER 57  •  Subarachnoid Hemorrhage  535

Skin incision Burr holes and bone cuts

Selfretaining retractor

Lateral cerebral (sylvian) sulcus Temporal lobe

Frontal lobe

R. temporal lobe (retracted)

Oculomotor (III) n.

Aneurysm R. internal carotid a. R. ophthalmic a. Aneurysm

R. middle cerebral a.

R. anterior cerebral a. Optic chiasm

Aneurysm

L. ophthalmic a.

Lateral cerebral (sylvian) sulcus

L. internal carotid a. L. anterior cerebral a.

Thalamostriate a.

Aneurysm Anterior communicating a. L. recurrent a. (of Heubner)

Operating microscope

Olfactory tract

R. frontal lobe (retracted)

Figure 57-10  Frontotemporal Approach for Internal Carotid, Ophthalmic, Anterior Communicating, and Middle Cerebral Aneurysms.

Cerebellar tonsil (retracted)

Skin incision Glossopharyngeal (IX) and vagus (X) nerves (retracted) Posterior inferior cerebellar artery Portion of occipital bone removed Posterior arch of atlas removed Upper portion of arch of second cervical vertebra removed

Aneurysm Accessory (XI) nerve (retracted) Dura mater Vertebral artery Dentate ligament C2

Figure 57-11  Posterior Approach for Vertebral and Posterior Inferior Cerebellar Aneurysms.

536  SECTION XII  •  Cerebrovascular Diseases

are occluded or injured is completed just before clipping. Once secured, the aneurysm can be punctured to allow it to collapse and relieve mass effect if present. Adjuncts to the surgical treatment of aneurysms are beyond the scope of this text but include temporary clipping, cerebral bypasses, aneurysmorrhaphy, and, in some cases, full hypothermic cardiac arrest. With microsurgical technology and various temporary and permanent aneurysm clips available and the establishment of skull base and revascularization techniques, management of once inoperable lesions has become routine.

Endovascular Therapy The treatment for ruptured intracranial aneurysms requires multidisciplinary efforts; the core team consists of an interventional neuroradiologist, vascular neurosurgeon, neurointensivists, and rehabilitation specialists. Recently the endovascular approach has emerged as an alternative treatment modality for selected aneurysms. In the treatment of complex large and giant aneurysms, endovascular therapy may serve as an adjunct to surgical interventions. Although there are singular reports of aneurysm treatments from Ciniselli, Moore, and Werner in the last 150 years that resemble modern endovascular therapy, the current treatment modality was originally devised by Guglielmi in 1990 using platinum coils that were detached within the aneurysm dome using an electrolytic mechanism. Approved by the Food and Drug Administration in 1991, the device became known as Guglielmi detachable coil (GDC). Presently coils that incorporate other materials and utilize alternative detachment mechanisms are available in the United States. The international subarachnoid aneurysm trial (ISAT) is currently the only large-scale international prospective randomized controlled trial (RCT) comparing surgical clipping with endovascular treatment of ruptured aneurysms. The authors demonstrated a 24% relative and 7.4% absolute reduction of death or dependency at 1 year in favor of coiling. A number of criticisms of this publication have been made, specifically the applicability of the findings to the practice pattern found in the United States and a perceived imbalance between the experience of the endovascular practitioners and the surgeons in the study. Endovascular treatment for ruptured intracranial aneurysms is usually conducted under general anesthesia. Systemic heparinization during the procedure is preferred by some but is not universally accepted. A 6 or 7 French guide catheter is introduced via the femoral artery into the internal carotid artery (ICA) or vertebral artery to provide a stable platform. A microcatheter is advanced over a microguidewire coaxially through the guide catheter into the aneurysm, and a series of soft platinum coils are deployed sequentially until radiographic occlusion of the aneurysm dome is achieved. Coils used for aneurysm embolization are usually MR compatible, and MR imaging may be used for noninvasive follow-up imaging. The shape, size, and neck diameter of the aneurysm in relation to the parent vessel determine whether or not its dome can be successfully occluded. Larger or odd-shaped aneurysms with wide necks are more difficult to occlude completely. In ISAT the proportions of completely, subtotally (with remnants at the neck), and incompletely occluded aneurysms at follow-up were

66%, 26%, and 8%, respectively. It is not clear what the risk of rebleeding is from a small neck remnant following either endovascular coil embolization or rarely surgical clipping. Post-clip angiography shows that only 4–10% of aneurysms have any major remnant while coiling achieves complete aneurysm occlusion in only 50% of cases. When near-complete occlusions are included, this level increases to 85–90%. Another limitation to endovascular procedures is an approximately 16–32% aneurysm recurrence depending on the location, degree of compaction, and morphology of the aneurysm when primarily treated (Fig. 57-12). Patients may require repeated treatment or even surgical intervention with removal of the coils. More recent modifications in device technology aim to achieve safer and more durable treatment of a larger proportion

A

B

AP vertebral artery angiogram showing compaction of coils in a basilar tip aneurysm over time and regrowth of the aneurysm base (patient in the second vignette). Figure 57-12  Basilar Tip Aneurysm Re-expansion.



of aneurysms, including those with a wide neck or complex shape that were not readily amenable to occlusion with GDC platinum coils alone. These include complex coil shapes that conform better to irregular aneurysm geometries, balloon remodeling techniques (a nondetachable balloon catheter deployed across the aneurysm neck and inflated to prevent herniation of the coils into the parent vessel), stent-assisted coil embolization, bioactive coils coated with polyglycolic polylactic acid to enhance thrombus formation and organization, platinum coils coated with a polymeric hydrogel that swells when in contact with blood to achieve greater packing density, and radioactive coils. Liquid embolization systems with high-density Onyx (Ethyl-vinyl alcohol copolymer mixed with micronized tantalum powder) deliver a mass of highly viscous and cohesive material into the aneurysm, ideally leading to complete occlusion of the aneurysm and covered stents aimed to restore the parent vessel wall in its entirety. Many of these technologies have been studied in selected patients and are currently under review for approval in the United States. Interval posttreatment angiographic follow-up, either with noninvasive CT or MR angiography or catheter angiography, is mandatory and should be performed lifelong. There are no clear guidelines regarding the most appropriate follow-up intervals, and an individualized approach may be taken. Overall procedure-related morbidity is 6–19%, and mortality 1–2%. Procedural complications include aneurysm rupture (2– 5%) potentially leading to worse outcome or death, thromboembolic events (5–9%), parent vessel occlusion (2.5%), coil migration 0.5%, and significant groin hematomas (0.6%). Long-term complications of coil embolization include recanalization and coil compaction. Even after complete radiographic occlusion of the aneurysm, only about 25–35% of its volume consists of coils, with the rest being thrombus. About 10% of coiled aneurysms will require a second treatment after recanalization to ensure stability. The risk of rebleeding has been documented at 0.2% per patient year with a mean follow-up of 4 years, similar to the rebleeding rates after neurosurgical clipping.

CHAPTER 57  •  Subarachnoid Hemorrhage  537

The risk of postoperative epilepsy, though low in absolute terms, is lower after endovascular treatment compared to craniotomies. The relative risk reduction of coiling compared to surgery at 1 year is 47.9%, and the absolute risk reduction is 3.9%. Embolization materials are more expensive than aneurysm clips, but health economic data emerging from the ISAT suggests that these excess costs are offset by shorter hospital stays, fewer dependent survivors, less requirement for rehabilitation, and possibly reduced neuropsychological impact. The development and clinical experience with the Guglielmi detachable coil technology is extensive, and follow-up is available beyond 10 years. In many patients, aneurysm endovascular coil occlusion is a valuable alternative to surgery. Overall, 82% of patients experience favorable outcomes. ADDITIONAL RESOURCES Allen GS, Ahn HS, Preziosi TJ, et al. Cerebral arterial vasospasm—a controlled trial of nimodipine in patients with subarachnoid hemorrhage. N Engl J Med 1983;308:619-624. This study was conducted in intact neurologically stable patients. Extrapolating these findings to those presenting with deficits and critically ill patients requires caution. Bederson JB, Ward I, Wiebers DO, et al. Recommendations for the management of patients with unruptured intracranial aneurysms: a statement for healthcare professionals from the Stroke Council of the American Heart Association. Stroke 2000;31:2742-2750. Eskridge J, Song J, and participants. Endovascular embolization of 150 basilar tip aneurysms with Guglielmi-detachable coils: results of the food and drug administration multi-center clinical trial. J Neurosurg 1998;89: 81-86. International Study of Unruptured Intracranial Aneurysms Investigators. Unruptured intracranial aneurysms: risk of rupture and risk of surgical intervention. N Engl J Med 1998;339:1725-1733. International Subarachnoid Hemorrhage Aneurysm Collaborative Group. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2,143 patients with ruptured intracranial aneurysms: a randomized trial. Lancet 2002;360:1267-1274. Pivotal randomized study that has established the use of endovascular coiling as a less invasive, safe and efficacious alternative to surgical clipping. MacDonald RL, Wallace MC, Kestle JR. The role of angiography following aneurysm surgery. J Neurosurg 1993;79:826-832.

Intracerebral Hemorrhage Kinan K. Hreib

Clinical Vignette A 72-year-old woman with history of hypertension noticed tingling in the right arm. Within 30 minutes, her right leg buckled and she fell. Her husband helped her up and she was able to walk without support. She rested, but within an hour, she developed speech difficulties and more definite right-sided weakness. She was brought to the emergency department (ED) and was noted to have mild right arm weakness and some wordfinding difficulties. Her blood pressure was 140/80 mm Hg. She got up to go to the bathroom, walked approximately 10 ft, and collapsed on the floor. She was then globally aphasic, with left gaze deviation (i.e., paralysis of gaze to the right) and right hemiplegia. Within 10 minutes, she became gradually unresponsive. She was intubated for airway protection and taken for brain CT scanning, which demonstrated a large left putaminal hemorrhage. Soon thereafter, she had bilaterally dilated fixed pupils. The vestibular-ocular reflexes were lost. Within another 10 minutes, she was determined brain dead.

T

he preceding vignette demonstrates the classic presentation of a primary intracerebral hemorrhage (ICH with a rapidly evolving focal neurologic deficit). Its progressively increasing size led to increased intracranial pressure with coma from downward herniation of the uncus onto the brainstem and ultimately irreversible neurologic damage. The only means to prevent ICH is appropriate therapy of its major risk factor, hypertension. There are two forms of intrinsic cerebral hemorrhage, primary ICH, which has a predilection to affect the striatum, thalamus, midbrain, pons, and cerebellum, and subarachnoid hemorrhage (Chapter 57). ICH comprises approximately 10% of all strokes in the Caucasian population and up to 20% in the Asian population. Over the past several years, improved treatment of hypertension has decreased the number of patients experiencing ICH. Hypertension is a major risk factor for intracerebral hemorrhages in patients between the ages of 40 and 70. A small proportion of intracerebral hemorrhages in patients older than age 60 years is not directly related to hypertension and is primarily caused by amyloid angiopathy. Furthermore, the increased use of oral anticoagulant therapy in the elderly population has led to higher rates of warfarin-associated ICH. Warfarin anticoagulation increases the risk of intracerebral hemorrhage fivefold, and some studies have estimated that 18% of intracerebral hemorrhages admitted to the hospital are related to its use. Of interest is that most bleeds in patients on warfarin occur when the INR is within the recommended therapeutic limits. Secondary, less common causes of intracerebral hemorrhages include primary and metastatic tumors of the brain and in younger

58 

individuals cerebral hemorrhage associated with underlying arterial venous malformation or cavernous angioma.

PATHOPHYSIOLOGY OF HYPERTENSISVE PRIMARY ICH Intracranial hemorrhage is a rapidly evolving process that may progress over hours or days. The pressure effects of the initial hemorrhage lead to mechanical disruption and tearing of surrounding vessels with subsequent gradual expansion of the hematoma out from the original center. Rebleeding is the most feared early complication of ICH and occurs in approximately 40% of patients. Rebleeding usually occurs within the first 24 hours but, on occasion, has been reported up to a week later. The underlying pathological mechanism of primary hypertensive ICH is attributable to either the formation of miliary microaneurysms or primary arteriolar degeneration (lipohyalinosis and weakening of the blood vessel intima and media wall layers) (Fig. 58-1). The presence of miliary aneurysms is directly related to hypertension but is not necessarily the initial site of bleeding, and cases of hypertensive ICH outside the areas of microaneurysms have been noted. This suggests that degeneration of the arteriolar smooth muscle wall is likely an important factor in the evolution of ICH. Hypertensive intracerebral hemorrhages have a predilection to occur in the basal ganglia and the thalamus. The arterioles in these structures are likely more vulnerable to degenerative changes brought on by diffuse, large pressure pulses over time. Although hypertension is considered an important risk factor for ICH, studies are inconsistent in estimating the exact risk of ICH in hypertensive patients. It has been noted in some studies that up to 90% of patients with ICH have evidence of hypertension at the time of presentation. Other important risk factors include smoking, alcohol consumption, black race, and low total serum cholesterol levels. The latter is likely to be an anomaly of population studies. Patients with ICH and concomitantly low serum cholesterol levels tend to be older than age 80 years and, on average, have higher diastolic pressures. The effect of lower cholesterol levels, particularly LDL, on increasing the incidence of ICH is likely small and the mechanism remains unclear; whether it is causative or an epiphenomenon of another process warrants further investigation.

CLINICAL PRESENTATION Intraparenchymal hemorrhages vary in presentation depending on the site of the bleeding (Fig. 58-2). In approximately 60% of patients, neurologic symptoms develop gradually or stepwise over a period of hours. To some extent, the location and size of the hematoma predict clinical outcome. Headache occurs at presentation in approximately 40% of patients with ICH. Less commonly, headache develops within a



CHAPTER 58  •  Intracerebral Hemorrhage  539

B. Microaneurysm ruptures,

causing pressure on adjacent (satellite) vessels.

A. Microaneurysm formed in parenchymal artery of brain as result of hypertension. Lenticulostriate vessels (shown) most commonly involved, but similar process may occur in other parts of brain, especially lobar white matter, thalamus, pons, and cerebellum.

C. Satellite vessels rupture.

D. Amount of blood extravasated into

brain tissue depends on tissue turgor opposed to intravascular blood pressure.

Moderate-sized intracerebral hemorrhage involving left putamen, with rupture into lateral ventricle; brain distorted to opposite side; scar of healed hemorrhage on right side

CT scan showing large putaminal hemorrhage Figure 58-1  Hypertensive Intracerebral Hemorrhage: Pathogenesis.

few days after the ictus. Intracerebral hemorrhages presenting with headache are often located at the brain surface or within the cerebellum. Depression in the level of consciousness and vomiting occur in 50% of patients, particularly those with large cerebellar bleeds. Seizures occur at onset in up to 10% and are seen most commonly with lobar bleeds in the anterior circulation. There are rare incidences of patients with deep hemorrhages having seizures. The subsequent risk for seizures in ICH patients is up to 29% for those with lobar hemorrhages but only 4% for those with deep hemorrhages. Other symptoms seen in association with ICH include low-grade fever without obvious infection, cardiac arrhythmias, and dysautonomia, especially with pontine bleeds. A description of some of the most common symptoms at different sites of ICH follows.

Deep Supratentorial Hemorrhage PUTAMINAL HEMORRHAGES

The most common site of ICH is the putamen, and these are classified into anterior, middle, and posterior lesions. Anterior putaminal hemorrhage often causes motor weakness due to compression of the anterior limb of the internal capsule. If the ICH is on the left, abulia and aphasia are common accompaniments. When the lesion occurs on the right, significant behavioral changes can occur, including disinhibition, poor insight

and judgment, and occasionally violent behavior. Caudate hemorrhages are associated with similar behavioral and cognitive changes. Studies suggest that these behaviors result from frontal lobe disconnection. Often, deficits from small anterior putaminal hemorrhages are reversible. A hemorrhage within the midputamen, however, results in severe deficits, often with poor recovery. In this case, ICH compresses and undercuts nearby cortical structures, causing global aphasia if involving the left hemisphere and severe neglect if involving the right. With posterior putaminal hemorrhages, a combination of sensory-motor deficits, visual field difficulties, limb ataxia, and behavioral changes often results. Some putaminal hemorrhages not extending into the globus pallidus present with short-lived hemichorea or hemiballismus, although a variety of other abnormal involuntary movements have been described. Large or medially located putaminal hemorrhages and head of the caudate hemorrhages can dissect toward the ventricle, with resultant intraventricular hemorrhage and the development of acute obstructive hydrocephalus with rapid deterioration due to increased intracranial pressure. Primary intraventricular hemorrhage, in contrast, does not affect surrounding brain tissue, and most cases present as a nonlocalizing rapidly progressive syndrome of nausea, vomiting, stupor, and seizure. In less acute cases, the patient presents with headaches, confusion, and somnolence.

540  SECTION XII  •  Cerebrovascular Diseases

Pathology

Caudate nucleus (blood in ventricle)

CT scan

Pupils

Eye movements

Motor and sensory deficits

Other

Sometimes ipsilaterally constricted

Conjugate deviation to side of lesion; slight ptosis

Contralateral hemiparesis, often transient

Headache, confusion

Putamen (small hemorrhage)

Normal

Conjugate deviation to side of lesion

Contralateral hemiparesis and hemisensory loss

Aphasia (if lesion on left side)

Putamen (large hemorrhage)

In presence of herniation, pupil dialated on side of lesion

Conjugate deviation to side of lesion

Contralateral hemiparesis and hemisensory loss

Decreased consciousness

Thalamus

Constricted, poorly reactive to light bilaterally

Both lids retracted; eyes positioned downward and medially; cannot look upward

Slight contralateral hemiparesis, but greater hemisensory loss

Aphasia (if lesion on left side)

Occipital lobar white matter

Normal

Normal

Mild, transient hemiparesis

Contralateral hemianopsia

Pons

Constricted, reactive to light

No horizontal movements; vertical movements preserved

Quadriplegia

Coma

Cerebellum

Slight constriction on side of lesion

Slight deviation to opposite side; movements toward side of lesion impaired, or sixth cranial nerve palsy

Ipsilateral limb ataxia; no hemiparesis

Gait ataxia, vomiting

Figure 58-2  Intracerebral Hemorrhage: Clinical Manifestations Related to Site.

THALAMIC HEMORRHAGES

Clinically, thalamic ICHs are classified into posterior–inferior, posterior–lateral, and dorsal–medial. Somnolence is one of the most common presentations of medial–posterior and inferior thalamic bleeds and can be profound as a result of bilateral disruption of the rostral reticular activating system. If the hemorrhage dissects anteriorly, often persistent hypokinetic behavior results from disconnection of the frontal lobe. With inferior–lateral thalamic hemorrhage, there is weakness and clumsiness and, occasionally, tremors and choreoathetoid movements. Tremors are likely related to disruption of projections from the cerebellum and dentate nucleus. Disruption of the fibers of the ansa lenticularis are likely responsible for the choreoathetoid movements. More lateral thalamic hemorrhages involving the ventral posteromedial and ventral posterolateral thalamic nuclei

primarily cause unilateral sensory symptoms but occasionally motor involvement when the hemorrhage extends laterally to involve the internal capsule. Eye movement abnormalities, small pupils, ptosis, chorea, and dystonia also occur. Hematomas involving the dorsal-medial thalamic area present with prominent memory problems and behavioral changes thought to relate to dissociated frontal cortex, cingulate gyrus, and amygdalar connections. Speech and language deficits are the least consistent symptoms of thalamic hemorrhages. Paraphasia, naming difficulties, or a perceived inability to comprehend, with preservation of repetition, is typical of thalamic aphasia. In patients with right thalamic hemorrhage, deficits mimic cortical lesions with neglect or hemi-inattention, vivid visual, and, less often, auditory hallucinations can occur in the days following thalamic ICH.



SUPERFICIAL LOBAR HEMORRHAGES

After the putamen, the most common site of primary ICH is one of four locations in the cerebral cortex. The parietal and occipital areas are most frequently involved. In general, hypertension is an important risk factor for all ICH regardless of location, but whether blood pressure plays a lesser role in the contribution of lobar versus subcortical hemorrhages remains inconclusive. Primary amyloid angiopathy frequently underlies nonhypertensive intracerebral lobar hemorrhage. Other less common causes include vascular malformations, primary and metastatic malignancies, sympathomimetic drugs, anticoagulants, irreversible antiplatelet and fibrinolytic agents, and sinus thrombosis with venous infarctions and bleeds. Lobar hemorrhages often present with headaches and vomiting. Seizures at the onset of lobar hemorrhage are common, particularly those within the posterior parietal or frontal lobe. Functionally, patients with lobar hemorrhage may have better outcomes than those with deep hemorrhages. However, prognosis depends on hematoma size, level of consciousness at presentation, and presence of intraventricular blood. Mortality rates range from 12 to 30% in superficial lobar hemorrhages compared to 25–42% in deep basal ganglionic and thalamic hemorrhages and up to 97% in pontine hemorrhages. • Frontal hematomas. Intracranial hemorrhages in the superior aspect of the frontal lobe are usually small and cause weakness in the contralateral leg. Inferior frontal hemorrhages are larger, causing a depressed level of consciousness, hemiplegia, hemisensory deficits, and horizontal gaze paresis. Language output can also be affected. Apathy and abulia occur with superior mesial lesions and may be prominent. • Parietal hematomas. With right hemispheric hemorrhages, often the most striking clinical presentation is a cortical neglect syndrome, while left hemispheric hemorrhages produce various degrees of aphasia. Extension into subcortical areas often occurs with weakness, and hemianopsia is frequently seen. More medial hemorrhages result in downward pressure on the upper brainstem and can cause obtundation or coma. • Occipital hematomas. Although headaches are prominent in many lobar hemorrhages, those occurring with occipital hemorrhage are particularly severe. The most obvious neurologic deficit is a homonymous hemianopsia but some patients present with other visual changes, including flashes of bright lights and palinopsia (afterimages). Other deficits indicative of more anteriorly located hemorrhage include visual extinction, dysgraphia, and dyslexia. Occipital hematomas are the least likely to be related to hypertension. • Temporal hematomas. Neurologic deficits in temporal hematomas differ depending on the side involved. Fluent aphasia, often associated with paraphasia and poor comprehension, is the most prominent deficit from isolated left temporal lobe hemorrhage. In contrast, right temporal hemorrhages are often associated with relatively minor problems, most commonly confusion. Other neurologic symptoms depend on whether there is extension into the surrounding subcortical areas or adjacent frontal lobe.

CHAPTER 58  •  Intracerebral Hemorrhage  541

Infratentorial Hemorrhages CEREBELLAR HEMORRHAGE

Clinical Vignette A 58-year-old woman with substantial history of arterial hypertension presented to the ED with a 1-hour duration of acute-onset headache, gait unsteadiness, and left arm incoordination. On examination, the patient was alert and oriented but had left-sided dysmetria, gait ataxia, and left CN-VI and CN-VII palsies. Her BP was 200/110 mm Hg. Urgent head CT showed a 3-cm cerebellar hemorrhage with slight compression of the fourth ventricle. Antihypertensive treatment aiming for a MAP of 100–120 mm Hg was initiated. Within 30 minutes after the CT scan, the patient’s level of consciousness deteriorated, necessitating intubation. She was brought immediately to the operating room for evacuation of the hematoma and responded well. One month later, her examination was remarkable for only mild clumsiness of the left arm and a slightly wide-based gait.

As in the preceding vignette, patients with cerebellar hemorrhages can deteriorate rapidly, even “in front of one’s eyes,” but can still respond exceptionally well with expeditious surgical intervention. Most cerebellar hemorrhages are associated with hypertension. However, approximately 10% of primary cerebellar hemorrhages are caused by AVM, tumors, blood dyscrasias and the use of warfarin anticoagulation. Headache, spinning vertigo, nausea, vomiting, and, most commonly, unsteady gait characterize the typical presentation. Some headaches are occipital, but many involve the orbital and supraorbital areas. The most reliable symptoms of a hemispheric cerebellar hemorrhage include headache, vomiting, nystagmus, ipsilateral limb ataxia with, at times, ipsilateral peripheral CN-VI and CN-VII palsies and horizontal nystagmus. The less common vermian hemorrhages often resemble a pontine hemorrhage and can progress rapidly to coma, making it difficult to identify specific early clinical signs that can differentiate one from the other. Cranial nerve palsies are related to involvement of adjacent pontine structures or stretching secondary to increased cerebellar pressure. In hypertensive bleeds involving the vermis or the cerebellar hemispheres, the superior cerebellar artery is most often involved. Unlike supratentorial bleeds, in which a small hemorrhage is often well tolerated, infratentorial ICH within the posterior fossa often leads to rapid neurologic deterioration and death. Close monitoring in an ICU for 36–48 hours, when the risk of deterioration is at its highest, is therefore recommended for most patients. Rebleeding, rupture into the fourth ventricle, and accelerated hemorrhagic edema, alone or in combination, often lead to a devastating outcome. Hemorrhages larger than 3 cm may extend into the fourth ventricle and lead to the development of acute hydrocephalus and require ventriculostomy placement. The threshold for surgical evacuation of the hematoma should be low and considered at the earliest sign of deterioration. The major goal is decompression of the posterior fossa to prevent blockage of the fourth ventricle and compression of

542  SECTION XII  •  Cerebrovascular Diseases

the adjacent brainstem. Fortunately, if impending brainstem compression is recognized early, there are often only minimal residual deficits after surgery, even with extensive cerebellar evacuation and decompression. The potentially positive recovery from cerebellar hemorrhages and decompressive surgery reflects that the deep cerebellar nuclei, crucial for gait coordination and balance, are often spared from direct damage. PONTINE/MIDBRAIN HEMORRHAGE

Pontine and midbrain hemorrhages are relatively uncommon but have the most devastating outcome compared with other sites of primary intracranial hemorrhages. Three distinct vascular territories dictate the clinical presentation. The paramedian penetrators, arising directly from the basilar trunk, are the primary arteries supplying the midline pons or midbrain. ICH in this location causes bilateral damage and is often fatal. Sudden onset of deep coma, quadriparesis, ophthalmoplegia, and bilateral papillary abnormalities are the presenting signs. Another group of small arteries, the short circumferential penetrators, courses laterally, supplying the lateral basis pontis, where a hemorrhage may predominantly cause unilateral bulbar symptoms with profound dysphagia. The third important group of vessels, the long circumferential arteries, arises from the anterior–inferior cerebellar artery and primarily supplies the lateral tegmentum. ICH within this segment leads to relatively minor symptoms, including facial numbness and ataxia secondary to involvement of the spinal trigeminal and vestibular nuclei. However, involvement of the intrinsic pontine nuclei, such as the cochlear and facial nuclei, are also affected, which leads to a more serious outcome. Pontine hemorrhages often have a relatively gradual clinical presentation evolving over hours. Neurologic deficits, including horizontal gaze palsies, miotic sluggishly reactive pupils, quadriparesis, and coma, are the expected clinical signs. Certain unique eye findings, including ocular bobbing and the one-and-a-half syndrome, provide excellent diagnostic clues to pontine hemorrhages. Some patients also exhibit twitching of the limbs and face and rippling of torso muscles. Dysautonomia with irregular pulse, erratic breathing patterns, and an increase in body temperature have also been observed. Vivid, sometimes frightening, formed hallucinations, called peduncular hallucinosis, occur relatively often in patients with involvement of the midbrain tegmentum.

SECONDARY INTRACEREBRAL HEMORRHAGE ICH not directly caused by hypertension is encountered with vascular malformations, hemorrhagic transformation of ischemic stroke, anticoagulants, as well as fibrinolytic agents or irreversible antiplatelet therapy (Box 58-1). Primary amyloid angiopathy is often the underlying cause of nonhypertensive lobar hemorrhage. Less common causes include primary and metastatic malignancies, sinus thrombosis with venous infarctions and bleeds, acquired or inherited coagulopathies, induced or autoimmune vasculitides and systemic granulo­ matous disorders, central infectious processes, and trauma (Box 58-2).

Box 58-1  Common Causes of Intracerebral Hemorrhage 1. Primary intracerebral hemorrhage Hypertension Idiopathic 2. Vascular malformations Aneurysm Arteriovenous malformation Cavernous angioma 3. Embolic infarct 4. Anticoagulant therapy

Box 58-2  Uncommon Causes of Intracerebral Hemorrhage* 1. Endocarditis 2. Venous sinus thrombosis 3. Malignancy: primary, metastatic 4. Blood diathesis DIC, ITP, TTP Leukemia Multiple myeloma Sickle cell disease 5. Other hematologic disorders, particularly coagulopathies Hemophilia von Willebrand factor deficiency Afibrinogenemia 6. Vasculitis Polyarteritis nodosa Systemic lupus erythematosus Wegener granulomatosis Takayasu arteritis Temporal arteritis Chemical vasculitis Primary CNS vasculitis Sympathomimetics (amphetamine, cocaine, phenylpropanolamine) 7. Systemic disorders Sarcoidosis Behçet syndrome CNS infections, particularly herpes zoster 8. Trauma *DIC, disseminated intravascular coagulation; ITP, idiopathic thrombocytopenic purpura; TTP, thrombotic thrombocytopenic purpura.

In most cases of ICH, especially when hypertension is absent, follow-up imaging studies are essential to investigate the possibilities of underlying predisposing pathology. Contrastenhanced brain MRI scanning performed about 3 months later, after extravasated blood has been allowed to reabsorb, may uncover an underlying lesion initially obscured by the acute hematoma. Occult vascular malformations were possibly the most underdiagnosed causes of lobar hemorrhages prior to CT and MRI scanning and were frequently missed by early angiography due to the presence of clot and mass effect on the brain. They were diagnosed only during surgical or pathologic specimen inspection after hematoma removal. The most common occult vascular lesions include small AVMs and cavernous angiomas (Fig. 58-3A–D).



CHAPTER 58  •  Intracerebral Hemorrhage  543

Thalamic Hemorrhage Secondary to AVM

A

Primary CNS Mixed glioma Epidermoid cyst Pituitary adenoma Oligodendroglioma Ependymoma Choroid plexus papilloma Meningioma Craniopharyngioma Glioblastoma Astrocytoma

B

CT with left thalamic hemorrhage and blood in ventricles.

Lateral view; vertebral angiogram with thalamic AVM

Cavernous Hemangioma

C

Box 58-3  Tumors Causing Intracerebral Hemorrhage*

D

Metastatic Melanoma Kidney Lung Breast Osteogenic sarcoma Ovary Colon *In order of frequency.

CT with small acute hemorrhage in the left medial temporal lobe close to the lateral ventricular horn (arrow).

T2-weighted MR with variable intensity pattern and black halo (paramagnetic effect of iron, Fe3+) (arrow).

Hemorrhagic Transformation With Intravenous tPA Therapy.

E

Axial CT showing large right MCA territory infarction (hypodensity) with moderate mass effect.

F

Comparable axial CT 11 days post stroke and intravenous tPA therapy showing multiple small petechial hemorrhages (arrows).

Figure 58-3  Common Causes of Intracerebral Hemorrhage.

Hemorrhagic brain infarct (HBI), in contrast to primary intracranial hemorrhage, is a secondary phenomenon that occurs as a result of ischemic damage to both the brain parenchyma and the vessel wall distal to the site of occlusion. The vascular wall endothelium and the blood–brain barrier are subsequently damaged and leak with reperfusion as they no longer tolerate normal arterial pressure. Petechial bleeding and, at times, gross hemorrhage through the damaged vessel into the infracted area may be seen (Fig. 58-3E&F). It is estimated that

petechial bleeding develops in more than 50% of patients with embolic infarcts. Although it is often implied that cardioembolic strokes are more likely to be associated with development of HBI, some investigators suggest that any large infarct, regardless of mechanism, is predisposed to such bleeding. The use of IV heparin or heparinoid for secondary stroke prevention also promotes the development of HBI. However, the presence of petechial hemorrhage without frank hematoma formation does not seem to worsen neurologic outcome. Along with typical subarachnoid hemorrhage, aneurysmal rupture can, at times, cause intraparenchymal hematoma with focal neurologic signs (Fig. 58-4A&B). The location of the blood often hints to the site of the aneurysm. Lateral temporal lobe hematomas suggest MCA aneurysmal rupture while medially located bleeds are associated with carotid artery aneurysms. Frontal hematomas indicate anterior communicating artery aneurysm. Posterior communicating artery aneurysms cause thalamic hemorrhages, often with intraventricular extension. Primary or metastatic brain tumors can lead to ICH (Box 58-3; Fig. 58-4C&D). A single small hemorrhage from a metastatic lesion, as can be seen with melanomas or hypernephromas, may be difficult to distinguish from primary ICH unless evidence of other lesions is identified. Other clues, such as an atypical cortical or subcortical location of the bleed, irregular margins, and unexpected contrast enhancement of the lesion must prompt further investigations to exclude systemic disorders. A detailed dermatologic examination may reveal irregularly pigmented lesions, suggesting melanoma, and ultrasound or body CT scan may uncover a renal tumor.

Antithrombotic- and AnticoagulantInduced ICH The question of whether aspirin promotes ICH remains unclear, but the Physicians’ Health Study, a randomized, double-blinded,

544  SECTION XII  •  Cerebrovascular Diseases

A. CT with blood in left sylvian fissure.

B. Lateral left internal carotid angiogram with small

C. CT showing dense right frontal subcortical mass

D. CT showing small left frontal hemorrhage in a

with edema representing a hemorrhagic colon cancer metastasis.

distal MCA aneurysm (arrowheads).

patient with leukemia and bleeding diathesis.

Figure 58-4  Uncommon Causes of Intracerebral Hemorrhage.

placebo-controlled trial looking at aspirin in cardiovascular disease, suggested a trend toward increased risk. There were 2.1% hemorrhagic strokes in the treatment group and 1.1% in the placebo group. This increase was not seen in many other clinical trials testing the benefits of aspirin for the prevention of stroke. Several trials using warfarin for stroke prevention in patients with atrial fibrillation have demonstrated intracerebral bleeding rates of 0.5–1.8 per year. The highest risk for bleeding was seen in patients older than age 75 years. The combination of warfarin and aspirin suggested similar rates of systemic bleeding, approximately 2.4 per year, and no difference in rates of ICH. The use of intravenous heparin in the setting of acute stroke has not been systematically studied as to benefit or complications. A few studies have suggested no risk of ICH whereas others indicated a risk of approximately 2%, especially when heparin is used in the setting of an acute stroke. The International Stroke Trial used subcutaneous heparin at 12,500 U twice daily versus 5000 U twice daily or a combination of subcutaneous heparin and aspirin. At 14 days, the risk of ICH was 1.8% for the high heparin dose and 0.7% for the low heparin dose. Rates were similar when heparin was combined with aspirin. Heparinoid formulations as well have shown a risk of ICH of 2.4% versus 0.8% for controls.

Amyloid Angiopathy Amyloid angiopathy is an uncommon arteriolar and venular vasculopathy with hyaline eosinophilic depositions and

subsequent weakness of the vessel wall and microaneurysm formation. It is the cause of ICH in 10% of patients age 60 years or older and 20% in patients older than age 70 years. The usual areas of ICH are lobar, both in the subcortical area and the cortex, routinely sparing the basal ganglia, the thalamus, and the brainstem. In the Dutch and Icelandic familial forms of amyloid angiopathy, the mean age for ICH occurrence is as young as 30 years of age. In contrast to the nonfamilial form, ICH in the familial forms of amyloid angiopathy may also affect the brainstem and the cerebellum along with the more typical cortical and subcortical loci. MRI evidence of previous asymptomatic small hemorrhages is encountered in many patients (Fig. 58-5). However, cases of rapidly successive, small intracranial hemorrhages within a short time period with progressive disability and death have been described. The presence of subcortical white matter disease seen on CT or MRI scans may be a reflection of chronic ischemia from amyloid-laden arterioles. These changes may suggest a higher risk for future hemorrhages and therefore a more cautionary approach to anticoagulation or the potential use of thrombolytic agents is advised.

Endocarditis The true incidence of endocarditis is unknown. Rheumatic heart disease was formerly the primary cause of bacterial endocarditis, with the most common agent being Streptococcus viridans. More virulent forms of endocarditis have emerged as the use of intravenous drugs has increased. Furthermore, the use of



CHAPTER 58  •  Intracerebral Hemorrhage  545

A. CT with moderate-sized left frontal hematoma with edema.

B. GRE MRI shows high-intensity lesion with a C. GRE MRI showing multiple small paramaghypointense rim representing blood products.

netic lesions consistent with multiple small previous hemorrhages (arrows).

Figure 58-5  Amyloid Angiopathy.

implanted long-term catheters or other similar devices, particularly in hemodialysis or immunocompromised patients, has increased the risk of infection. Native valve acute endocarditis usually has an aggressive course, with Staphylococcus aureus and group B streptococci the typical organisms. Underlying structural valve disease need not be present. Subacute endocarditis due to alpha-hemolytic streptococci or enterococci usually occurs in the setting of structural valve disease and has a more indolent course. Staph. aureus and fungal infections are surpassing streptococcal bacteria as causes for valvular infection. Mitral and aortic valves are especially vulnerable. The mitral valve is more consistently associated with neurologic complications than is the aortic valve. In one study, more than 28% of those with bacterial endocarditis had neurologic complications. Mortality was 77% with staphylococcal infections and 36% with streptococcal infections. Cerebral infarc­ tions occurred in up to 50% of patients, ICH occurred in 2.1%, and subarachnoid hemorrhage in 0.8%. Bacterial mycotic aneurysms are often small and located peripherally, unlike berry and fungal mycotic aneurysms found at the bifurcations in the circle of Willis. Corresponding ICH is therefore typically located superficially in the more distal part of the vessels. However, the more peripheral locations are not necessarily less devastating than the more typical deeper hemorrhages. The presumed hemorrhage mechanism is pyogenic arteritis resulting in blood vessel wall erosion and rupture or rupture of mycotic aneurysm (present in only 12% of patients). Patients receiving anticoagulation as treatment of a presumed ischemic stroke were more likely to suffer hemorrhages. ICH occurred in 24% of patients receiving anticoagulation in the setting of ischemic infarcts or TIAs caused by endocarditis. Repeated blood culture and transesophageal echocardiography are the cornerstones of diagnosis in endocarditis and, if both are positive, have a sensitivity higher than 90%. Varied clinical profiles of TIA, stroke, and subarachnoid hemorrhage typify the presentation of an atrial myxoma. Therefore, a cardiac embolic evaluation, including transesophageal echocardiography and electrocardiography, are needed.

Vasculitis Although systemic necrotizing vasculitides, usually associated with peripheral complication such as mononeuritis multiplex, are rarely the cause of cerebral infarction or hemorrhage, primary CNS angiitis is commonly associated with both. The disease course is subacute and presents with mental status changes, headaches, focal deficits, and seizures. Systemic lupus erythematosus is another disorder with a variable degree of CNS involvement. Autopsy series, however, suggest a high frequency of subarachnoid hemorrhage and, to a lesser extent, intracerebral and subdural hemorrhages.

Moyamoya Moyamoya is a rare primary angiopathy of unknown etiology associated with cerebral vascular occlusive disease due to fibrocellular thickening of the intima and thinning of the media. The carotid siphons and the proximal middle cerebral arteries are typically involved with numerous small vessels developing around the site of occlusion, usually at the base of the circle of Willis. Two forms of Moyamoya exist, the familial and atherosclerotic form. The familial form is most commonly seen in Japan and affects children aged around 10 years. These children often experience recurring bouts of hemiplegia or aphasia. Some symptoms may stutter or progress over a few weeks. The atherosclerotic form occurs in older patients, who may present with recurring TIAs or ICHs. Early in the disease, symptoms may be difficult to interpret, and MRI findings are often unspecific. Careful observation for flow voids within the major vessels may demonstrate abnormalities that can prompt further investigation with angiography. ICH occurs mostly in the older-patient form because of small friable vessels sprouting within the basal ganglia.

Arteriovenous Malformation Prevalence of arteriovenous malformation (AVM) is unknown, but estimates range from 1 to 2 per 100,000 individuals. Luckily

546  SECTION XII  •  Cerebrovascular Diseases

only 10% become symptomatic from bleeding. Patients often present with headaches, TIA-like spells and seizures. The risk of bleeding from an AVM is estimated at 3% per year. However, the risk of rebleeding in the first year is as high as 30%. AVM with associated aneurysmal lesions, poorly developed venous drainage, and location near the ventricles hold a higher risk for bleeding. Management of symptomatic AVMs includes surgical decompression and removal of the AVM, if it is accessible. Other interventions include a combination of catheter-based intervention plus surgery. Small vascular malformations may be treated with focused radiation, although the latter approach may take years to obliterate the malformation. Brain swelling and hemorrhage may complicate treatment because of altered flow dynamics. Some experts advocated treatment of the malformation in stages to allow the brain and the malformation to adjust gradually to changes in blood flow.

Cerebral Cavernous Angioma This vascular malformation is either inherited or sporadic. Single lesions are seen in the sporadic form whereas the inherited form often presents with multiple lesions. In the familial form of the disease, three genes have been identified, CCM1/ KR1T1, CCM2/MGC4607, and CCM3/PDCD10. Large clusters of family members with cavernous angioma have been identified in Hispanic-American families. Often this condition presents with TIA-like spells, seizures, or headaches. Lesions that are diagnosed on MRI are frequently shown to have bled in the past. When bleeding from cavernous angioma is significant, the morphologic features of the lesion may be obscured, making diagnosis acutely difficult. Repeat imaging studies, once there is some resolution of the hematoma, may ultimately help reveal the lesion.

MANAGEMENT AND PROGNOSIS Many ICH patients initially presenting with a modest neurologic deficit may rapidly worsen during the first 24 hours. Serial CT scans demonstrate that ICH can recur or worsen even up to 7 days after the ictus. As in the first vignette of this chapter, recurrent or progressive ICH is often rapid and fatal, particularly if the hemorrhage extends to the ventricular system and produces acute hydrocephalus. Sudden volume increase, and mass effect from enlarging ICH compromises the surrounding microvasculature and leads to both mechanical and ischemic tissue damage to the surrounding brain structures. Tissue shifts compounded by evolving vasogenic cerebral edema over 24 hours may lead to transtentorial herniation. Excessive increases in blood pressure, concomitant infection, fever, hyperglycemia or hypoglycemia, and other medical conditions all worsen outcome. The initial management of ICH, after ensuring adequate ventilation and hemodynamic stability, involves correcting coagulopathies, treating hypertension, and addressing the possibility of increased intracranial pressure. In patients with intraventricular blood and early hydrocephalus, placement of a temporary external drain should be considered. Beyond these basics principles, the best treatment of ICH remains unclear and quite variable from center to center and in different countries. Although some advocate invasive techniques for

hematoma evacuation, others rely mostly on medical treatment and supportive care. At present, there are no strict recommendations for blood pressure control in the setting of primary hypertensive ICH. There is evidence to indicate that elevated BP greater than 210 mm Hg is associated with recurrent or expanding ICH but lower BP measurement may not be. Indeed, far too aggressive lowering of BP may lead to a potential drop in cerebral perfusion pressure (CPP), especially in the presence of elevated ICP, and cause secondary ischemia with worsening outcomes. The present guidelines set by the American Heart Association/ American Stroke Association council suggest definite treatment of SBP above 210 mm Hg or of MAP of 150 mm Hg with a continuous infusion of a titratable IV medication such as nicardipine, a beta-blocker, or nitroprusside if needed. For measurements below this level but above 180 mm Hg systolic or MAP of 130 mm Hg and in the presence of suspected ICP, a decrease of BP to keep the CPP above 60 mm Hg is recommended. If ICP is not present, careful monitoring with an attempt to avoid hypertensive episodes is suggested. It is often useful to obtain patients’ prior BP measurements from outpatient records or from primary care providers if available. This may help guide blood pressure control by providing a sense of where each individual patient’s BP range of cerebral autoregulation was before the ICH. Surgical Trial in Intracerebral Hemorrhage (STICH, 2005) was a multicenter international prospective randomized trial to compare early surgery with initial conservative treatment for patients with spontaneous supratentorial intracerebral hemorrhage. In this study, no overall benefit from early surgery when compared to conservative treatment could be demonstrated. Surgery demonstrated slightly better outcome (26.1% vs. 23.8%), but survival rates appeared to be similar in surgically and medically treated patients. Subgroup analysis suggested that large hemorrhages, older age, and blood in the ventricles predicted poor outcome. Also the subgroup with superficial bleeds and no intraventricular hemorrhage tended to fare better with surgery than with medical treatment alone (49% vs. 37%). The outcome from surgery likely depends on several factors, including the fact that deep-seated basal ganglia or thalamic hemorrhages are difficult to evacuate without disrupting surrounding normal structures and exacerbating brain damage, especially with open craniotomy. A trial to evaluate the role of early surgery in superficial supratentorial lobar hematomas without intraventricular hemorrhage is ongoing. However, when a nondominant hemispheric or cerebellar ICH threatens impending herniation and before the patient’s level of consciousness signi­ ficantly deteriorates, emergent surgery may be lifesaving and may provide a reasonably good recovery, especially in younger patients. Patients who have small hematomas (smaller than 30 cm3) seem to do generally well without surgical evacuation. However, larger hematomas (larger than 60 cm3) do poorly, even when evacuated surgically. Hematomas between 30 and 40 cm3 may do best after surgical evacuation. There is no evidence that minimally invasive surgery (microsurgery or endoscopy) hold any advantage over open craniotomy, and the advantage of these technique is yet to be determined. A few neurosurgical studies have investigated the benefits of evacuating deep hematomas



using a continuous infusion of thrombolytic agents and suction method. Thrombolytic agents such as tissue plasminogen activator have been infused into the hematoma. Although they produce more rapid hematoma resolution, the long-term clinical outcome seems unchanged. Generally, the therapeutic approach must be individualized. Rebleeding and hematoma expansion is a common cause of acute deterioration and holds up to a 70% risk of death or unfavorable outcome. Prevention of hemorrhage progression, therefore, has become a central theme in the acute treatment of primary ICH. To that end, pro-coagulants, such as activated Factor VII, have been tested in patients with intracerebral hemorrhage (Factor Seven for Acute Hemorrhagic Stroke [FAST]). Activated Factor VII initiates the clotting cascade by binding to the surface of platelets and generating aX, which, in turn, induces surface thrombin formation. This reaction is specific to the site of bleeding as Factor VII works in the presence of tissue factor released at the site of injured tissue. A safety study in 2005 demonstrated that patients treated within 3 hours of presentation with activated Factor VII had the hematoma increase only by 11–16% compared to a 29% increase in the placebo group. Mortality in this Phase II trial decreased from 29 to 18%. Clotting events such as myocardial infarctions, deep venous thrombosis, pulmonary emboli, and ischemic strokes increased from 2% to 7%. A Phase III trial demonstrated that Factor VIIa did indeed decrease ICH volume, but failed to show a clinical effect with mortality and severe disability rates found comparable in the treatment groups and the placebo group. It was postulated that age might have played a role in diluting out the result and that relatively healthy individuals below the age of 70 years may be the ideal patients to respond to such treatments. At this time, however, no pharmacological treatment is available to limit the expansion of the spontaneous intracerebral hemorrhage in the absence of a coagulopathy. Expansion of the hematoma or rebleeding in patients taking warfarin is another difficult management issue. Obviously, reversing the effects of warfarin is the first step in trying to limit bleeding. The administration of vitamin K and freshfrozen plasma is often given acutely, but the benefits are not realized for another 24 hours. Some have advocated the use of prothrombin complex concentrate a (conglomerate of high levels of vitamin K–dependent factors) or activated Factor VII to help reverse the effects of warfarin. However, as mentioned previously, there is a significantly increased risk of thromboembolic events, and there are no studies at this time to help guide such treatment. SUMMARY

The overall mortality of patients with ICH is approximately 50% with lobar and basal ganglionic bleeds and up to 75% when involving the brainstem. Of those who survive, only half will achieve independent living. Initial presentation is predictive of outcome. Individuals who present with coma and signs of

CHAPTER 58  •  Intracerebral Hemorrhage  547

herniation have poor prognoses. Rapid increase in intracranial pressure with concurrent brainstem Duret hemorrhages leads to irreversible reticular activating system damage and coma. Patients in whom intraventricular blood leads to hydrocephalus do not fare well either, with 90% suffering poor outcomes or death. The size of the initial hematoma, as defined by CT, is also predictive. There is a mortality rate of approximately 50–75% in patients with more than 40 mL of blood on CT at presentation. If the patient survives the bleed, the ultimate neurologic recovery depends on the hemorrhage location and residual deficits. ADDITIONAL RESOURCES Caplan LR. Caplan’s Stroke: A Clinical Approach. 3rd ed. Woburn, Mass: Butterworth-Heinemann; 2000. Broderick J, Connolly S, Feldmann E, et al. Guidelines for the management of spontaneous intracerebral hemorrhage in adults: 2007 update: a guideline from the American Heart Association/American Stroke. Stroke 2007 Jun;38(6):2001-2023. Evidence-based guidelines to help manage intracerebral hemorrhage and its complications. Dennis MS. Outcome after brain haemorrhage. Cerebrovasc Dis 2003; 16(Suppl 1):9-13. Fisher CM. Pathological observations in hypertensive cerebral hemorrhage. J Neuropathol Exp Neurol 1971;30:536-550. Garcia JH, Ho KL. Pathology of hypertensive arteriopathy. Neurosurg Clin North Am 1992;3:497-507. Garibi J, Bilbao G, Pomposo I, et al. Prognostic factors in a series of 185 consecutive spontaneous supratentorial intracerebral haematomas. Br J Neurosurg 2002;16:355-361. Kaneko M, Tanaka K, Shimada T, et al. Long term evaluation of ultraearly operation for hypertensive intracerebral hemorrhage in 100 cases. J Neurosurg 1983;58:838-842. Kase CS. Intracerebral hemorrhage: non-hypertensive causes. Stroke 1986;17:590-595. Mayer SA. Intracerebral hemorrhage: natural history and rationale of ultra early hemostatic therapy. Intensive Care Med 2002;28(Suppl 2): S235-S240. Mayer SA, Brun NC, Begtrup K et al. Recombinant activated factor VII for acute intracerebral hemorrhage. N Engl J Med 2005:352(8):777-785. Mayer SA, Brun NC, Begtrup K, et al. Efficacy and safety of recombinant activated factor VII for acute intracerebral hemorrhage. N Engl J Med 2008 May 15;358(20):2127-2137. Treatment with rFVIIa within 4 hours of ICH reduced hematoma volume growth but did not improve survival or functional outcome. Also, there were higher rates of arterial thrombotic events in the higher-dose group. Morgenstern LB, Frankowski RF, Shedden P, et al. Surgical treatment for intracerebral hemorrhage (STICH): a single-center, randomized clinical trial. Neurology 1998:51(5):1359-1363. This clinical study has influenced our approach to surgical evacuation of ICH with most neurosurgeons and neurologists considering it as generally showing lack of benefit for hematoma evacuation. However, a subset of patients with superficial ICH and no intraventricular blood emerged as potentially benefiting from surgical evacuation and are currently being randomized to STICH II. Skidmore CT, Andrefsky J. Spontaneous intracerebral hemorrhage: epidemiology, pathophysiology, and medical management. Neurosurg Clin North Am 2002;13:281-288. Woo D, Broderick JP. Spontaneous intracerebral hemorrhage: epidemiology and clinical presentation. Neurosurg Clin North Am 2002;13: 265-279.

Trauma to the Brain

59 

Carlos A. David and Jeffrey E. Arle

T

raumatic brain injury (TBI), occurring worldwide in relation to various types of civilian and armed forces accidents, is one of the most common mechanisms for serious lifelong morbidity or mortality. Within the United States, one person sustains a head injury every 15 seconds. The societal loss is devastating as the majority of these injuries involve individuals entering adulthood with great promise only to be cut down, often with irretrievable injuries that leave them dependent for their remaining lives. For example, within the United States there are 2 million cases of traumatic head injury annually; 100,000 die within hours, 500,000 require hospital stays, and up to 100,000 have permanent disability. Whether it is a cycling, skiing, or relatively uncommon contact sports injury, or result of an impulsive acceleration while negotiating a challenging roadway to impress peers with one’s driving prowess, or on a battlefield such as currently occurs in Iraq or Afghanistan, the consequences are the same: a very promising or accomplished life has lost all its future potential. Various head injury classification systems exist. These include (1) severity (mild, moderate, severe), mechanism (closed vs. penetrating), (2) skull fractures (depressed vs. nondepressed), (3) presence of intracranial lesions (focal vs. diffuse), and (4) hemorrhages, that is, extra-axillary epidural or subdural, subarachnoid, or focal parenchymatous lobar, or brainstem Duret hemorrhage.

Clinical Vignette An otolaryngologist requested an expeditious neurologic evaluation of a very vigorous octogenarian who was so fit that he downhill skied 3 weeks earlier; this patient reported recent-onset sense of “spinning vertigo” and cloudiness of vision, precipitated by sudden standing or neck extension. Additionally, he was experiencing new-onset headaches that were becoming increasingly severe and were awakening him from his sleep. Concomitantly he was having difficulty with mental concentration and hand coordination, as well as a feeling of “weak legs.” On further questioning, he recalled that 7 weeks earlier he had slipped on the ice, striking his occiput, while helping to push an auto out of a snow bank. On examination, he had moderately severe difficulty performing tandem gait (something most healthy 70-year-olds often cannot perform, but this was probably abnormal in this athletic man). The remainder of his neurologic examination was normal. Head computed tomography (CT) demonstrated large biparietal subdural hematomas. Bilateral craniotomies were performed, draining both hematomas. Except for a few focal motor sensory seizures, occurring only in the immediate postoperative period and responding well to phenytoin, his recovery was otherwise excellent. Comment: This gentleman presented a classic history for subdural hematoma. Initially he had disregarded a

moderately significant closed head injury as there were no immediate sequelae other than for a modest scalp contusion. He was symptom-free for 5 weeks. This patient’s initial symptoms were not very impressive because his brain compensated well. Despite a careful neurologic examination, the tandem ataxia was his only neurologic abnormality. This could easily be dismissed as appropriate for age; however, the entire clinical picture was classic for a subdural hematoma until proven otherwise as defined by the CT scans.

GENERAL PRINCIPLES OF HEAD INJURY CARE The initial management of severe head injuries, as for any serious trauma victim, includes the “ABC” evaluation for Airway, Breathing, and Circulation and a careful general and neurologic examination. • A—airway: Suction to free pharynx from blood and other material; intubate after cervical spine evaluation. • B—breathing: Evaluate rate, rhythm, and breath sounds; ventilate to raise PaO2 and reduce PaCO2 (to lower intracranial pressure [ICP]); monitor arterial blood gas levels. • C—circulatory status: Start intravenous infusion of normal saline solution, followed by blood if indicated; obtain immediate laboratory work and x-rays; administer steroids and phenytoin, plus pressor agent if required (shock rarely due to head injury alone; search for cause). Concomitantly, the patient’s general level of responsiveness must be assessed using the Glasgow Coma Scale (Fig. 59-1). The lowest possible score of 3 means that individuals have no ability to open the eyes, no motor response to verbal command or direct stimuli, and no verbal response to the physician’s questions, giving a score of 1 or nil for each of the three components. The highest possible score is 15. Soft tissue injuries are commonly associated with more severe head injuries. A complete examination of the exterior surface of the face and head is vital. Blood loss can be extensive given the location of blood vessels within the dense connective tissue of the scalp, which decreases retraction of cut vessels and promotes bleeding.

SKULL FRACTURES These can be located in the calvaria (vault) and/or the basal skull. Fractures of the cranial vault carry a 20 times greater incidence of intracranial hematoma in comatose patients and a 400 times greater incidence in conscious patients. Basal skull fractures, often difficult to identify on head CT, can present with pathognomonic signs, including raccoon or Panda bear eyes, battle signs (ecchymosis over the mastoid), and cerebrospinal fluid (CSF) leakage from the nose, throat, or ears (Fig. 59-2).

E Spontaneous . . . . . 4

Eye opening (E) Open your eyes

To speech . . . . . . . 3 To pain . . . . . . . . . 2 Nil . . . . . . . . . . . . 1

To pain2 Response to speech3

Spontaneous4

Nil (no response)1

Motor response (M) Show me 2 fingers

Extensor response2

Abnormal flexor response3 Obeys6

Localizes5

M Obeys . . . . . . . . . . 6 Localized . . . . . . . 5 Withdraws . . . . . . 4 Abnormal flexion . . . . . . . . . 3 Extensor response . . . . . . . . 2

Withdraws4

Nil . . . . . . . . . . . . 1

Nil (no response)1

Oriented . V. . . . . . . 5

Verbal response (V) Scream, groan, moan

Yesterday Mother

What year is this?

Inappropriate words3 Confused 1997 conversation4

2011

Incomprehensible sound2

Oriented5

Confused conversation . . . . . 4

No response

Inappropriate words . . . . . . . . . . 3 Incomprehensible sounds . . . . . . . . . 2

Nil 1 Nil . . . . . . . . . . . . 1 Coma score (EMV)3 to 15

Figure 59-1  Glasgow Coma Scale.

C

B A

“Panda bear” or “raccoon” sign due to leakage of blood from anterior fossa into periorbital tissues. Absence of conjunctival injection differentiates fracture from direct eye trauma.

Longitudinal (A) and transverse (B) fractures of petrous pyramid of temporal bone, and anterior basal skull fracture (C)

Figure 59-2  Basilar Skull Fractures.

Rhinorrhea

Battle sign: postauricular hematoma

Otorrhea or ear hemorrhage

552  SECTION XIII  •  Trauma

Signs suggesting need for operation in head injuries Emergency Early Indriven fragments of bone

Decrease in level of consciousness or increased restlessness

“Ping-pong ball” depression of skull in an infant Development of unilateral pupil dilatation and/or ocular palsy Rhinorrhea or otorrhea; persistent or recurrent Urinary incontinence in previously continent patient Hemiplegia, hemiparesis, hemianesthesia, Babinski sign

Fracture depressed more than 1/2 thickness of skull

Decreasing pulse rate

Increasing blood pressure

Spicule of bone in venous sinus

Deterioration in vital signs Figure 59-3  Signs Suggesting Need for Operation.

Most leaks resolve spontaneously. Persistent leaks necessitate operative treatment (Fig. 59-3). Depressed fractures, and those along the temporal bone, are more commonly associated with injury to the brain or blood vessels. A fracture line across the middle meningeal artery may predispose to an epidural hematoma. Open fractures with their communication between the intracranial vault and the external environment are associated with higher risks of spinal fluid leaks and infection (Fig. 59-4).

EXTRA-AXIAL TRAUMATIC BRAIN INJURIES Traumatic Subarachnoid Hemorrhage This is the most common sequela of TBI and is typically associated with other types of intracranial lesions. Subarachnoid hemorrhage (SAH) can range from clinically insignificant to fatal.

These SAH blood products can obstruct CSF reabsorption, leading to increased intracranial pressure (ICP) with hydrocephalus. Treatment of SAH often involves placement of ventricular drains and shunting systems for secondary hydrocephalus.

Epidural Hematomas These represent an acute blood collection contained between the dura and inner table of the skull. These occur in approximately 2% of TBIs (Fig. 59-5). Epidural hematomas (EHs) most commonly develop in the temporal and parietal regions; 90% of EH are associated with a skull fracture. Arterial lacerations, particularly of the middle meningeal artery (Fig. 59-6) or, less commonly, venous injuries, initiate the formation of hematomas. Contiguous lacerations of the dura mater allow this blood into the epidural space.



CHAPTER 59  •  Trauma to the Brain  553

Left lateral skull film showing left frontal depressed skull fracture

Elliptical incision with extensions to remove devitalized skin and pericranium

Left lateral skull film revealing occipital depressed skull fracture

Burr hole placed at margin of fracture to facilitate elevation of depressed bone fragments. Bone edges, dura, and brain then debrided

Compound depressed skull fracture. Note hair impacted into wound

Watertight dural closure. Optionally, bone fragments may be cleaned and wired in place Skin is closed in one layer

Figure 59-4  Compound Depressed Skull Fractures. Temporal fossa hematoma Shift of normal midline structures

Skull fracture crossing middle meningeal artery

Compression of posterior cerebral artery Shift of brainstem to opposite side may reverse lateralization of signs by tentorial pressure on contralateral pathways.

Herniation of temporal lobe under tentorium cerebelli

Subfrontal hematoma

Compression of oculomotor (III) nerve leading to ipsilateral pupil dilatation and third cranial nerve palsy

Compression of corticospinal Herniation of cerebellar and associated pathways, resulting in contralateral tonsil hemiparesis, deep tendon hyperreflexia, and Babinski sign

Frontal trauma: headache, poor cerebration, intermittent disorientation, anisocoria

Posterior fossa hematoma Occipital trauma and/or fracture: headache, meningismus, cerebellar and cranial nerve signs, Cushing triad

Figure 59-5  Epidural Hematoma.

Immediately after the closed head injury, the patient “typically” experiences an initial but relatively brief loss of consciousness secondary to the primary concussive injury. This is then followed by a lucid interval with return of wakefulness. Subsequently, as the torn vessels leak, an epidural hematoma develops and enlarges, leading to a rapid lapse into coma. Sometimes this entire process may transpire from injury, to transient loss of consciousness, and to a brief period of a “paradoxically reassuring alertness,” only to have a devastating, often irreversible,

coma develop within just 1 hour after the blunt head injury (see Fig. 59-3). However, this classic presentation occurs in less than one third of affected individuals. The actual rate of symptom progression depends on the type of associated brain injuries, their etiology, and the subsequent precise rate of blood accumulation within the epidural space. Cranial CT imaging usually demonstrates a hyperdense, biconvex collection between the skull and brain (Fig. 59-7). On occasion, the initial CT is normal as the hematoma has yet to

554  SECTION XIII  •  Trauma

Arachnoid granulations Opening of superior cerebral vein

Parietal (posterior) and frontal (anterior) branches of middle meningeal artery

Venous lacuna

Middle meningeal artery

Superior sagittal sinus Dura mater

Anterior meningeal artery (from anterior ethmoidal artery)

Mastoid branch of occipital artery

Anterior and posterior meningeal branches of vertebral artery Mastoid branch of occipital artery

Meningeal branches of ascending pharyngeal artery Tentorial branch (cut) and dorsal meningeal branch of meningohypophyseal trunk Middle and accessory meningeal arteries Meningeal branch of posterior ethmoidal artery Anterior meningeal artery (from anterior ethmoidal artery) Internal carotid artery and its meningohypophyseal trunk (in phantom) Middle meningeal artery Accessory meningeal artery Superficial temporal artery Maxillary artery Posterior auricular artery Occipital artery External carotid artery Figure 59-6  Meningeal Arteries and Dura Mater.

develop to a size that is definable. Thus when the patient is “at risk,” it is essential to be prepared to repeat the CT scan at the slightest change in clinical status. Once the EH is identified, emergency surgical evacuation is indicated. Any failure to recognize an epidural hematoma has a most significant mortality depending on patient age, time of treatment, hematoma size, and associated injuries.

Acute Subdural Hematoma These blood collections are located between the brain parenchyma and the dural membranes and are classified by their temporal profile. Acute subdural hematomas (SDHs) occur in 15% of TBI patients; these are seven to eight times more common than epidural hematomas. Older individuals are at greater risk because as the brain ages, there is an innate atrophy of the



CHAPTER 59  •  Trauma to the Brain  555

B. Epidural hematoma. CT scan A. Normal brain. CT scan demon-

strating normal anatomy at level of frontal horns of lateral ventricles (black arrows). Pineal gland (white arrow) is in normal midline location.

demonstrating hyperdense right parietal epidural hematoma (black arrows), which has assumed classic biconvex lens configuration secondary to adherence of dura to inner table of skull. Other structures are compressed and shifted.

C. Subacute subdural hematoma. CT scan demonstrating large isodense mass over left cerebral convexity. Compressed cerebral cortex (black arrows) shows enhanced density delineating inner border of subacute subdural hematoma. Normal structures are shifted across midline.

D. Acute intracerebral hematoma. CT scan demonstrating hyperdense mass in right parietotemporal area. Large acute intracerebral hematoma has shifted lateral ventricle toward midline. Blood is visualized within ventricular system (black arrow).

Figure 59-7  CT and Angiogram of ICH.

cerebral cortex. Thus in seniors, as the brain “normally” lessens in volume, an increasing space develops within their subdural compartment. In turn this leads to increased stretch on the bridging veins between the skull and the cerebral surface (Fig. 59-8). When any individual sustains direct head trauma, the brain parenchyma accelerates and decelerates in relation to fixed dural structures. This leads to a tearing of the now anatomically stretched veins that form a “bridge” between the cerebral cortex and the skull. Similarly concomitant injury to cortical arteries can also lead to bleeding into the subdural space (Fig. 59-9). CLINICAL PRESENTATION AND DIAGNOSIS

The initial severity of the injury determines the patient’s clinical presentation; this varies from neurologically intact, to altered mental states, subsequently associated with pupillary inequality and motor weakness, and eventually becoming comatose with signs of decorticate or decerebrate posturing. The lucid interval, a classical finding with epidural hematoma, is also commonly seen with acute SDH. Brain CT is the initial test of choice for detecting SDH and concomitant brain injuries. An acute SDH is recognized by its hyperdense crescent-shaped image between the brain and skull (see Fig. 59-7). Unlike epidural hematomas, SDHs typically cross skull suture lines, and sometimes extend along the falx cerebri. Head CT sometimes underestimates the size of the SDH given the similar imaging density of the nearby bone.

TREATMENT AND PROGNOSIS

If the patient has mental status changes or signs of focal cerebral compromise, beginning treatment of acute SDH as rapidly as possible with medical management for increased ICP and the associated cerebral edema using mannitol is very useful. Surgical intervention with a craniotomy is appropriate for individuals whose SDHs have mass effect, leading to focal neurologic deficits. Once a significant SDH is defined, surgical evacuation of the clot must be expeditiously performed. A burr-hole trephine evacuation is inadequate because the clot is often already more viscous than normal blood. Increased postoperative ICP occurs in almost 50% of SDH patients, and thus the initial medical management must be continued (Fig. 59-10). Residual and recurrent hematomas are also postoperative concerns. An acute SDH is often associated with a poor outcome. The combination of the hematoma with other injuries, particularly those affecting the brain parenchyma, is associated with a 50% mortality rate. Of those patients who do survive a significant number have permanent mental and physical disabilities. Outcomes are strongly predicted by patient age and initial presentation. Mortalities of 20% are recorded for individuals younger than 40 years, but this number increases to 65% for those older than this. This is a devastating lesion in senior citizens as there is an 88% mortality for octogenarians. The initial consciousness level also provides a prognostic guide. Conscious patients have a mortality rate of less than 10%, whereas unconscious patients have 45–60% mortality.

556  SECTION XIII  •  Trauma

Calvaria Pericranium Granular foveola Bridging vein Arachnoid Galea aponeurotica granulation Skin Falx cerebri

Superior sagittal sinus Emissary vein Diploic vein Tributary of superficial temporal vein Dura–skull interface (site of epidural hematoma) Dura mater Arachnoid–dura interface (site of subdural hematoma) Arachnoid Cerebral artery Subarachnoid space Pia mater Superior cerebral vein Cerebral hemisphere

Branches of middle meningeal artery

Superior sagittal sinus Dura mater Superior cerebral veins (bridging veins) (penetrating arachnoid and dura mater to enter superior sagittal sinus) Superior cerebral veins (beneath arachnoid) Superficial middle cerebral vein

Superior anastomotic vein (of Trolard) Inferior anastomotic vein (of Labbé)

Middle meningeal artery and veins

Inferior cerebral veins (beneath arachnoid)

Scalp, Skull, Meningeal, and Cerebral Blood Vessels Superior sagittal sinus Diploic vein

Arachnoid granulation

Emissary vein Frontal and parietal tributaries of superficial temporal vein Frontal and parietal branches of superficial temporal artery Arachnoid granulation indenting skull (foveola)

Cerebral vein penetrating subdural space to enter sinus (bridging veins) Epidural space (potential) Dura mater (two layers) Arachnoid Subarachnoid space Pia mater Middle meningeal artery and vein

Venous lacuna Inferior sagittal sinus Thalamostriate and internal cerebral veins

Figure 59-8  Superficial Cerebral Veins and Diploic Veins.

Deep middle and superficial temporal arteries and veins Deep and superficial middle cerebral veins



CHAPTER 59  •  Trauma to the Brain  557

CLINICAL PRESENTATION AND DIAGNOSIS

Section showing acute subdural hematoma on right side and subdural hematoma associated with temporal lobe intracerebral hematoma (“burst” temporal lobe) on left “Question mark” skin incision (black); outline of free bone flap and burr holes (red)

Skin flap reflected (Raney clips control bleeding); free bone flap removed and dura opened; clot evacuated by irrigation, suction, and forceps Figure 59-9  Acute Subdural Hematoma.

CHRONIC SUBDURAL HEMATOMA

These subdural blood collections commonly appear 2–3 weeks after an often seemingly innocuous injury, as illustrated in the initial vignette. Their incidence is 1–2 per 100,000 persons each year. Most chronic SDH patients are older than 50 years. Chronic alcoholics or patients with coagulopathies, particularly from iatrogenic sources such as anticoagulants, are more prone to bleeding with relatively minor trauma such as striking one’s head on the door frame on entering an automobile. Initially, relatively minor amounts of blood enter the subdural space after trauma or spontaneous hemorrhages. Subsequently, over a few weeks’ interval these blood products lead to a membrane formation at both the inner and outer aspects of the hematoma. Eventually, these membranes are prone to lowgrade bleeding and thus lead to slow enlargement of the SDH. Concomitantly a higher osmotic pressure develops within the subdural hematoma leading to an osmotic gradient that promotes passage of CSF into the initial SDH and consequently this mass lesion gradually enlarges. The clinical course is variable and not predictable. If the SDH reaches a critical size to compromise brain function, symptoms will develop. In contrast, a number of SDHs will slowly reabsorb without ever becoming symptomatic.

The presentation may range from subtle focal signs of cerebral compromise as determined by the site of injury such as aphasia, focal weakness or sensory loss, confusion, or seeming early dementia with bifrontal lesions, to those symptoms of the various herniation syndromes. A high clinical suspicion of SDH must always occur especially with the at-risk individual whenever there is remote history of head trauma. CT is the study of choice (see Fig. 59-7). Occasionally, a brain MRI serendipitously leads to a diagnosis of SDH in patients presenting with strokelike or seizure-type symptoms. TREATMENT AND PROGNOSIS

Medical management and observation is recommended for individuals with subtle clinical symptoms and signs: discontinuation of anticoagulant medications, close observation in a hospital or by a reliable adult, and serial CT. Surgical therapy is advisable for any chronic SDH that is causing significant mass effect or is associated with significant clinical morbidity. Up to 45% of chronic SDHs reaccumulate. Postsurgical mortality is approximately 10%. Unlike acute SDH, most chronic subdural patients are able to return to their previous levels of functioning although about 10% may develop seizures.

INTRA-AXIAL TRAUMATIC INJURIES Cerebral Contusions These are the second most common of the TBI lesions. Usually the frontal and temporal lobes are affected. Basically a contusion is a bruise to the brain tissue per se. These lesions are composed of hemorrhage, infarcted tissue, and necrosis. Coup lesions are those found under the sites of direct injury; contrecoup lesions are located at sides opposite to impact secondary to brain tissue necrosis and edema sites, where the brain decelerates against the skull (often the frontal and temporal poles). Cortical contusions are most common, but they also will occur within the deep white matter. Clinical presentation varies widely and is predicated on the location and size of the lesion. Many brain contusions enlarge during the first few days after injury. This can become very significant in patients who sustain high-impact trauma. Surgical intervention is usually not required for intracerebral contusions, especially for small, deep subcortical contusions; these are generally managed medically. However, larger lobar contusions with significant signs of mass effect sometimes require craniotomy and evacuation. Temporal lobe contusions are potentially the most dangerous given their location near the brainstem. Repeat CT scanning is essential to follow these lesions. Mortality rates for cerebral contusions range from 25% to 60%.

Intraparenchymal Hematomas About a quarter of head injury patients develop intraparenchymal hematomas: these are well demarcated areas of acute hemorrhage. The basic pathophysiology is similar to contusions. Most (90%) occur within the frontal and temporal lobes. Shear

558  SECTION XIII  •  Trauma

injury leads to deep cerebral white matter hematomas. Two thirds of intraparenchymal hematomas are also associated with concomitant subdural or epidural hematomas (see Fig. 59-9). An intraventricular hemorrhage, often complicated by hydrocephalus, may also commonly develop. Depending on the severity of the injury, almost half of these patients present with a loss of consciousness. Other signs and symptoms relate to the size and location of the hemorrhage. Medical management is the treatment of choice for deep or small hemorrhages and for unstable patients. Surgical resection is indicated for large superficial lobar hematomas associated with clinical signs of mass effect. Ventricular CSF drains also serve to monitor their ICP. These provide a means to follow neurologically severely compromised patients. Mortality rates vary from 25% to 75% in patients with an intraparenchymal hemorrhage. The eventual outcome of those who survive depends on their level of consciousness at presentation, size and location of hematoma, and severity of concomitant injuries. Lastly, age is a very important determiner of morbidity. The teenager may eventually have his or her posttraumatic parenchymal hemorrhage reabsorbed without significant residual neuronal damage. In contrast, the senior citizen may already have sustained age-related neuronal compromise and thus have a much diminished prognosis for reasonable return to a productive life.

Intraparenchymal monitor

Diffuse Axonal Shear Injury The combination of rotational acceleration and deceleration of the brain during traumatic impact results in shearing of both diffuse axonal pathways and small capillaries. High-speed motor vehicle accidents are the most common etiology in the civilian population. Very microscopic, penetrating blood vessels are damaged at multiple levels including the corticomedullary junction, corpus callosum, internal capsule, deep gray matter, and upper brainstem, leading to numerous small hemorrhagic foci. Early on, conventional CT scanning will not demonstrate any abnormality related to this type of lesion. The microhemorrhages may be best seen on gradient echoT2-weighted sequences (Fig. 59-11). Later there may be nonspecific white matter hyperintense lesions with atrophic changes. Shear injury is very commonly associated with other intraaxial and extraaxial traumatic insults, including focal hematomas. Shear injury is a major prognostic contributor to overall head injury morbidity. Often the initial brain CT is unremarkable, especially when there is no concomitant hematoma, as there are no specific findings associated with shear injury. However, during the first 48–72 hours after the injury, cerebral edema may become obvious. Small areas of punctate contusions can also be found in areas of diffuse axonal injury. The most common MRI finding

Intraventricular cannula

Subarachnoid pressure screw Epidural transducer

External ventricular drainage

Figure 59-10  Intensive Medical Management of Severe Head Injury.



CHAPTER 59  •  Trauma to the Brain  559

A. Restricted diffusion is quite prominent

B. Paramagnetic signal within corpus in left splenium of corpus callosum (arrow) callosum on gradient echo image confirms and less so involving left insular white matter associated petechial hemorrhage (arrow). (arrowheads).

C. Axial diffusion tensor image shows disruption of fibers (arrow).

Figure 59-11  Shear Injury.

is the presence of multifocal areas of abnormal signal (bright on T2-weighted images) at the white matter in the temporal or parietal corticomedullary junction or in the splenium of the corpus callosum. Patients with diffuse axonal injury often develop cerebral edema, with resulting increased ICP. Pressure monitors are required in patients whose clinical examination results are not reliable. Intraparenchymal monitors are usually used because the ventricles are often so compressed that ventricular catheter placement is difficult (see Fig. 59-11). It is this group of patients who may remain comatose for extended periods. This clinical picture is classified as a persistent vegetative state (Chapter 16). This entity carries an extremely poor prognosis (Fig. 59-12).

Condition is called persistent when it lasts without change for more than 1 month.

Patients may startle, look about, or yawn, but none of these actions are in conscious response to a specific stimulus.

Subarachnoid hemorrhage

POSTERIOR FOSSA LESIONS Cerebellar and posterior fossa traumatic brain lesions account for only 5% of post-TBI sequelae. Epidural hematomas, SDH, and intracerebellar hematomas are the most common traumatic lesions at this level. Because of the limited space within the posterior fossa, strategically placed lesions at this level can rapidly lead to early neurologic decline secondary to both brainstem compression and acute hydrocephalus. Careful assessment of patients for these injuries is critical, especially in high-risk individuals with basal skull fractures. MRI is the study of choice for detecting posterior fossa damage. Normal bony architecture, as imaged with brain CT, frequently prevents identification of posterior fossa lesions artifacts in patients with TBI. Therefore, evacuation of the hematoma with posterior fossa craniectomy is the primary treatment modality when there is a critical mass lesion (Fig. 59-13). In contrast, a ventricular drain is adequate for intraventricular bleeds.

Noncontrast brain CT demonstrating ominous sign of diffuse brain injury and possible prelude to a persistent vegetative state: sulcal effacement (diffuse edema) and subtle disappearance of normal differentiation between gray and white matter. Figure 59-12  Persistent Vegetative State.

560  SECTION XIII  •  Trauma

Drilling burr hole with Smith craniotome drill

Burr hole enlarged by rongeur, exposing epidural hematoma, which is being removed by suction

Figure 59-13  Exploratory Burr Holes and Removal of Posterior Fossa Hematoma.

TRAUMATIC BRAIN INJURY IN MILITARY COMBAT SETTINGS Significant effort has gone into defining appropriate guidelines of care for traumatic brain injury (TBI) since 1990. In 2005, Guidelines for Field Management of Combat-Related Head Trauma was offered by the Brain Trauma Foundation and also provides levels of evidence found in published literature supporting its conclusions. Nearly all of the supporting scientific literature is Class III evidence. Combat brain trauma tends to occur from high-velocity rifle rounds (as opposed to handguns) and penetrating shrapnel and debris, with or without blast injury. Yet, although there are differences in the circumstances and nature of brain traumas that occur within combat, the same general principles for managing both initial and ongoing care for TBI should be adhered to. This includes the maintenance of PO2 >90 mm Hg and systolic blood pressure >90 mm Hg, the use of mannitol or hypertonic saline if there is evidence of severe neurological dysfunction (Glasgow Coma Scale [GCS] score 90, the use of mannitol or hypertonic saline with evidence of severe neurologic dysfunction (generally GCS score right leg pain primarily precipitated with walking. The pain ceased whenever he stopped and rested for a few minutes … he did not even need to sit. With time, his pain was precipitated with significantly shorter distances, getting to the point where he could not go more than 100–150 yards without having to stop to relieve his discomfort. At rest he felt fine. He could not obtain an effective erection. This initially appeared to be a classic picture of intermittent claudication secondary to primary vascular disease. However, all of his peripheral pulses were normal. Doppler arterial evaluation was normal. His symptoms progressed; he could not mow his lawn or take walks and he felt weak climbing stairs. Lumbar spinal MRI and EMG were normal. He was than referred to us for a possible myopathy or spinal stenosis. His neurologic examination was perfect. All peripheral pulses were normal, and Doppler arterial studies, lumbar spinal MRI and EMG were normal. Vascular consultants did not feel that he had peripheral vascular disease. Psychiatric consultation found no psy­ chosomatic component. Exercise Doppler suggested mild decreased flow on the right. A repeat examination now demonstrated his peripheral pulses were no longer present. He now had a bruit over his left femoral artery CT angiogram demonstrated severe stenosis of the proximal left femoral and iliac artery (Fig. 63-1). Angioplasty and stenting led to immediate pain relief. Comment: This patient had classic intermittent claudi­ cation precipitated by exercise and totally relieved by rest. This almost always implies peripheral atheromatous disease. With his initially normal peripheral arterial evaluation he was thought to have a neurologic mechanism; however, this was not confirmed. Reevaluation demonstrated that he now had a femoral artery bruit. CT angiography identified proximal intrapelvic arterial compromise despite normal traditional techniques. This case particularly emphasizes the importance of revisiting the history and the examination with any patient whose clinical picture is not initially confirmed by traditional studies. The neurologist must always look at potential nonneurologic mechanisms whenever forming a differential diagnosis.

A 28-year-old milkman, who lifted many heavy milk cases daily, presented with low back pain. This had begun 1 year earlier after lifting an extra-large load, “wrenching” his back. Subsequently he noted gradually increasingly severe and eventually almost incapacitating low back pain that occasionally radiated into his buttocks and posteriorly down his right leg. He also noted increasingly more limiting early morning back and hip stiffness that gradually “loosened up” after he worked an hour. During the previous few months, his difficulties had progressed significantly. He now felt unable to finish his daily job responsibilities. Therefore he applied for workers’ compensation. Neurologic examination demonstrated complete loss of lumbar lordosis, significantly diminished chest excursion of only 1.5 cm (normal 3–6 cm), and mildly positive right straight leg testing. His neurologic examination was otherwise normal. An aortic diastolic murmur was presnt on cardiac examination. Spinal and hip radiographs demonstrated typical find­ ings of ankylosing spondylitis. These included significant sacroiliac joint sclerosis (Fig. 63-2). A serum HLA-B27 test was positive. A rheumatologist concurred with the diagnosis and began appropriate therapy. Comment: This patient sought care for a presumed jobrelated injury. Instead, a diagnosis of a serious rheumatologic disorder, namely ankylosing spondylitis, was made. If that diagnosis had not been appreciated at his age, eventually this would have led to serious spinal ankylosis with significant spinal immobility and possibly serious pulmonary compromise. Despite this early diagnosis of such a treatable condition, paradoxically this patient was disappointed with his care bacause he was no longer entitled to workman’s compensation!

T

he frequency of work- and accident-related back pain sometimes seems to be reaching pandemic proportions among workers performing heavy labor. Very often patients present with many potential causes for their back pain. These not only represent the classic well-defined organic mechanisms, such as lumbosacral nerve root compression, or ischemic compromise, but aditionally there may be many occupation-related

588  SECTION XIV  •  Radiculopathies and Plexopathies

B. Coronal CTA recon-

struction demonstrates beginning of high-grade stenosis from mixed plaque (arrowhead) to total occlusion (arrow).

A. Axial CTA demonstrates total occlusion of left common iliac artery (arrow).

Figure 63-1  Total Obstruction of Left Common Iliac Artery.

symptoms wherein overt or covert psychologic factors combine to provide a confusing milieu. Secondary gain issues are commonly confounding factors. It is vital not to impugn patients’ veracity by applying pejorative labels such as “hysteric,” “a crock,” “functional,” “litiginous,” or even “having psychological overlay.” Too often, these labels have led to inadequate evaluations, and serious illness is occasionally overlooked, as initially occurred in both of the above vignettes. Sincere physicians often encounter difficulties dealing with disingenuous patients seeking a “free ride” or a “green poultice” (Fig. 63-3). Most often secondary gain is the primary motivating factor, particularly with the perspective of a generous workers’ compensation settlement. However, the examining neurologist

A. A. Digital frontal radiograph of pelvis showing fusion (arrowheads).

must carefully evaluate each patient to search for a specific neurologic or other illness, as many patients understandably look for a simple explanation for their troubles—and it is easy to blame the workplace. Often the symptoms become embellished, not uncommonly subconsciously, to prove that a “workrelated injury” truly exists. Very often these patients tend to focus on their backs, seeking to prove the presence of a posttraumatic mechanically related disorder. They most definitely want to have their neurologist diagnose a specific work-related neurologic disorder as in the second vignette. Back pain patients may have psychosomatic features, but as with many organic disorders other primary psychologic disorders require consideration. These include depression,

B. T2-weighted fat-saturated coronal oblique view of sacrum demonstrates augmented T2 signal related to both SI joints (arrowheads).

Figure 63-2  Fusion of Sacroiliac Joints in 28-Year-Old Man with Ankylosing Spondylitis.



CHAPTER 63  •  Vascular, Rheumatologic, Functional, and Psychosomatic Back Pain  589

Facial expression may be flat, inappropriately unconcerned, or depressed rather than typically pained.

Vibration may be felt only on one side. Patient complains of severe back pain, which may radiate “all over.”

Complete hemianesthesia or glove-andstocking anesthesia may be present in conversion disorder or hypochondriasis/somatization.

Straight leg raising to 90° while patient seated, but

patient cannot tolerate same test when recumbent.

Sciatic nerve stretched

In some disorders, gait and posture may be dramatic, with exaggerated pain behavior, implying patient’s need to prove he is really sick.

No muscle atrophy despite prolonged disability

History may reveal family or work problems, symptoms of anxiety or depression, which patient identifies as secondary to physical problems but which may be primary.

The “green poultice”: Secondary gain, while often present, is seldom primary cause of pain and disability.

Normal response to raising one leg is to press down with other leg. Reverse response may occur in patients who are consciously or unconsciously manipulating examination.

Figure 63-3  Somatoform Back Disorders.

conversion disorder, psychophysiologic disorder, chronic pain syndrome, hypochondriasis, factitious disorder, and even schizophrenia. As the physician gains the patient’s confidence during the interview and examination, certain life stressors may become apparent, including family, job, personal issues, and inappropriate use of medications or even street drugs.

NEUROLOGIC EXAMINATION Each patient requires a comprehensive general neurologic examination, not only to evaluate the affected extremity and back but also to confirm that other neurologic systems and anatomic structures such as joints or vessels are healthy. There are specific clinical testing means that help distinguish an organic lesion from one that is embellished or inconsistent. The straight leg raise is an excellent example. A patient with organic

nerve root compression becomes uncomfortable when lying supine while the physician attempts to bring the patient’s leg to the perpendicular and is similarly affected when seated for a similar maneuver. Stretch on the sciatic nerve and its already compromised origins within the L5–S1 nerve roots initiates the discomfort. In contrast, an inconsistent response is often noted wherein individuals seeking secondary gain report pain with movement in the supine but not the seated posture. Another example is the well-known observation that when denervation occurs with significant peripheral nerve injury, it is followed by significant muscular atrophy. Such is generally lacking in the nonorganic setting. However, the quadriceps femoris is an exception; it may undergo significant disuse atrophy without a true peripheral nerve injury. Other useful clues and testing modalities can help to verify psychosomatic back pain (see Fig. 63-3).

590  SECTION XIV  •  Radiculopathies and Plexopathies

EVALUATION It is absolutely essential to carefully investigate patients’ concerns even when the clinician “is confident” of a psychosomatic or compensation disorder diagnosis. Too often such individuals are compartmentalized and put in the compensation diagnostic mode only to later be found to have a treatable disorder. Each of these patients needs their physicians to take their complaints with appropriate seriousness. This may mean ordering imaging studies such as MRI or, when MRI is contraindicated, CT/ myelography, neurophysiologic investigations including electromyography, evoked potentials, hip radiographs, and on occasion CT angiography. Finding a symptom-specific organic lesion that can be readily treated occasionally rewards the conscientious physician and patient alike. However, if the results of these investigations are all normal, the physician can appropriately reassure the patients that no organic mechanism is identified. When a true organic neurologic, musculoskeletal, or primary psychiatric disorder is excluded, only then should the physician consider psychologic mechanisms or secondary gain. A number of clues help in these diagnoses; perhaps the most important observation is the patient’s tendency to be “consistently inconsistent” in some features of the history or neurologic examination.

TREATMENT There are many rehabilitative and behavioral interventions that are supportive as well as often therapeutic for these patients. One needs to always maintain a supportive approach with such patients, no matter what the final diagnosis. This does not depend on whether a conversion disorder is diagnosed or a very subtle hint of a lumbosacral disc protrusion is suggested. Neither requires specific therapy especially a surgical one. Appropriate management combines reassurance, rehabilitative medicine techniques, group therapy, and, in the more refractive instances,

individual psychiatric intervention. An eclectic combination of various therapies often provides an improvement in long-term outcomes. Unfortunately, some individuals with chronic low back pain are subjected to multiple surgeries for less than reasonable indications. Thus they have no chance of improving because no specific lesion such as an extruded disc has been removed. Concomitantly these surgeries, per se, are then utilized to provide justification for granting disability status per se. The patient of course feels “there must have been” an organic work-related etiology for their difficulties if a surgeon “had to operate” on them. Another subset of individuals will continue to complain until a legal settlement is reached. They are identified as having the “green poultice syndrome” (see Fig. 63-3, bottom image). This is of course dependent on gaining a financial settlement; once that is accomplished it is not uncommon to see a rapid resolution of their symptoms and ability to return to their previous activities of daily living! ADDITIONAL RESOURCES Hayes J. Psychosomatic back complaints. In: Nervous System. Vol 1. Part II: Neurologic and Neuromuscular Disorders. Prepared by Frank Netter. West Caldwell, NJ: Ciba; 1986. p. 198. Jones HR. The Ciba Collection of Medical Illustrations. Henningsen P, Zipfel S, Herzog W. Management of functional somatic syndromes. Lancet 2007;369:946-955. Lindstrom-Hazel D. The backpack problem is evident but the solution is less obvious. Work 2009;32:329-338. Murphy PL, Volinn E. Is occupational low back pain on the rise? Spine 1999;24:691-697. Schultz IZ, Crook JM, Berkowitz J, et al. Biopsychosocial multivariate predictive model of occupational low back disability. Spine 2002;27: 2720-2725. Storm PB, Chou D, Tamargo RJ. Lumbar spinal stenosis, cauda equina syndrome, and multiple lumbosacral radiculopathies. Phys Med Rehabil Clin North Am 2002;13:713-733, ix. Tubach F, Beauté J, Leclerc A. Natural history and prognostic indicators of sciatica. J Clin Epidemiol 2004;57:174-179.

Brachial and Lumbosacral Plexopathies Ted M. Burns, Monique Ryan, and H. Royden Jones, Jr.

Clinical Vignette A 54-year-old man developed acute-onset right thigh, hip, and buttock pain. He also noted right knee “buckling” when he stepped off a curb, resulting in a fall. He also noted right foot drop. Paresthesias developed over the right thigh, shin, and foot. He required oral narcotics for pain relief. His past medical history was remarkable for type II diabetes mellitus, for which he took an oral hypoglycemic. His blood sugars had been under fair control. His review of systems was remarkable for a 30-pound weight loss over the past 3 months, which he attributed to renewed efforts at dieting. He doesn’t smoke or drink heavily. He is an attorney. Family history is negative. His general examination was unremarkable. His neurologic examination was notable for moderate weakness of right hip flexion, hip extension, knee extension, and ankle dorsiflexion. He has an absent right knee and ankle reflex, but reflexes are normal on the left lower extremity and upper extremities. Sensory testing demonstrates reduced vibration sensation at the right great toe and ankle. His gait is hesitant and reveals a right foot drop. Electromyography (EMG) demonstrated borderline right peroneal and tibial compound motor action potentials with normal velocities and distal latencies. The sural and superficial peroneal sensory nerve action potentials were absent on the right and normal on the left. Active denervation was present in right femoral and sciatic innervated muscles, and to a lesser extent in lumbosacral paraspinals and gluteal muscles. Magnetic resonance imaging (MRI) of the lumbosacral spine and pelvis was unremarkable, except for signal changes in denervating muscles. Lumbar puncture demonstrated an elevated cerebrospinal fluid (CSF) protein with normal cell count. Glycosylated hemoglobin was slightly elevated but otherwise his laboratory studies were normal. He was diagnosed with diabetic lumbosacral radiculoplexus neuropathy (also known as diabetic amyotrophy). After discussion of the pros and cons he was prescribed an empiric treatment trial of intravenous methylprednisolone.

T

he most important diagnostic tool for the evaluation of a possible plexopathy is a thorough and accurate history. The history-taking must be aided by a solid understanding of the risk factors for development of brachial or lumbosacral plexopathy. The most common etiologies of plexopathy are trauma, surgery (e.g., related to arm or leg positioning, injury with regional anesthetic block), birth injury, inherited genetic mutations (e.g., hereditary neuralgic amyotrophy), a primary autoimmune process (e.g., Parsonage–Turner, also known as neuralgic amyotrophy), previous radiotherapy, and neoplastic

64 

invasion (Fig. 64-1; Table 64-1). Systemic vasculitis and peripheral nerve sarcoidosis are other uncommon etiologies. Diabetes mellitus is a risk factor for an immune-mediated lumbosacral (and less often, brachial) plexopathy, that is, diabetic lumbosacral radiculoplexus neuropathy (diabetic LRPN) secondary to microvasculitis. Thus, if a prior or concomitant history of any of these risk factors (e.g., previous surgery, trauma, or family history, diabetes) is present, the clinician should strongly consider that etiology yet not necessarily forget to consider other plausible etiologies. It is also helpful to remember that recent infection, vaccination, and parturition are triggers for the immune-mediated plexopathies, especially brachial plexopathies (e.g., hereditary neuralgic amyotrophy and neuralgic amyotrophy). There are often other clues about etiology found in the symptomatology of the plexopathy. For example, the abrupt, spontaneous onset of shoulder and upper extremity symptoms favors an immune-mediated (e.g., microvasculitic) mechanism, such as that seen with hereditary neuralgic amyotrophy, neuralgic amyotrophy and diabetic cervical radiculoplexus neuropathy (diabetic CRPN), whereas a more gradual or insidious onset of symptoms would point toward neoplastic invasion or postradiotherapy plexopathy. Immune-mediated plexopathies (e.g., diabetic LRPN or neuralgic amyotrophy) usually begin with severe pain, lasting days to weeks, followed by the development of weakness a few days to a few weeks later. Radiation-associated plexopathy (e.g., for breast cancer) usually presents with much less pain than plexopathy due to malignancy or due to immunemediated mechanism. Radiation-induced brachial or lumbosacral plexopathy usually presents more gradually and can occur months to decades after radiotherapy. Recurrent, painful brachial plexopathy is most typical of hereditary neuralgic amyotrophy. The recognition of accompanying symptoms is also important. For example, weight loss is a common accompaniment of diabetic LRPN or diabetic CRPN, as well as plexopathies secondary to neoplasm or a more systemic process such as vasculitis. In the case presented above, the temporal evolution was of an abrupt-onset neuropathic process that caused motor and sensory dysfunction. The neuropathic process involved one lower extremity. The pain was so severe that the patient required narcotics. The patient had not experienced antecedent trauma, surgery, or radiotherapy. There was no family history of plexopathy. These factors suggested that an immune-mediated plexopathy was likely. Furthermore, the clinical setting was remarkable for diabetes mellitus and significant weight loss, and as diabetes mellitus is believed to be a risk factor for immune-mediated plexopathy and many of these patients experience contemporaneous weight loss, this diagnosis was most likely. Thus, the most likely etiology in this patient was DLRPN. Additional evaluation, including examination, electrodiagnostic testing and imaging, further supported the diagnosis (Fig. 64-2).

592  SECTION XIV  •  Radiculopathies and Plexopathies

From C4 Inflammation or immunization reaction Tears due to traction or wound

C5

Mechanism

Examples

Comments

C6

Trauma, traction

Motorcycle injury, cardiothoracic surgery Football etc. Mixed mechanisms

Often severe degree, poor prognosis Good prognosis Generally good prognosis Self-limited Recurrent, benign

C7

Constriction by scar Axillary n.

C8

Radial n. Musculocutaneous n.

T1 T2

Median n.

Table 64-1  Brachial Plexus Etiologies

Stinger Perinatal Idiopathic Hereditary Malignancy

Invasion by neoplasm Ulnar n.

Medial brachial cutaneous n.

Radiation

Autoimmune? Genetically determined Infiltration of tumor cells RoRx-induced ischemia

Medial antebrachial cutaneous n. Acute onset of pain in back of shoulder: inability to raise arm due to neuralgic amyotrophy

Knapsack, rucksack, etc Thoracic outlet

Compression

Heroin induced

Indeterminate

Entrapment

Poor prognosis Prognosis guarded but not suggestive of recurrent tumor Usually self-limited Rare, confused with CTS

CTS, carpal tunnel syndrome; RoRx, radiation therapy.

Tingling of fingers: edema of arm due to postmastectomy radiation scarring

Infant with traction birth injury: paralysis of right arm (Erb palsy)

Figure 64-1  Causes of Brachial Plexopathy.

CLINICAL PRESENTATION Plexus lesions commonly result in unilateral or asymmetric extremity muscle weakness and sensory complaints that do not conform to the distributions of single roots or nerves. Brachial plexopathies cause shoulder girdle weakness if the upper plexus is involved and hand weakness if the lower, or medial plexus is principally involved. Sensory loss is usually variable but follows a similar pattern; for example, a medial plexus lesion causes numbness of the fourth and fifth fingers. Autonomic

disturbances, caused by disruption of the sympathetic fibers traversing the lower trunk to the superior cervical ganglia of the brachial plexus, may be present and include trophic skin changes, edema, reflex sympathetic dystrophy (complex regional pain syndrome), and Horner syndrome (miosis, ptosis, ipsilateral facial anhidrosis). Upper plexus lesions of the lumbar plexus cause weakness of thigh flexion, adduction, and leg extension. Lower sacral plexus lesions result in weakness of thigh extension, knee flexion, and foot dorsiflexion and plantar flexion, and sensory changes. Complete lumbosacral plexopathy produces weakness and muscle atrophy throughout the lower extremity, with total areflexia and anesthesia. Concurrent autonomic loss results in warm, dry skin and peripheral edema. In addition to considering etiologies for plexopathy, the clinician needs to consider whether processes that may be mimicking plexopathy are likely considerations. The presence of neuropathic pain can reasonably exclude pure motor processes, such as motor neuronopathies (e.g., amyotrophic lateral sclerosis), disorders of neuromuscular junction transmission (e.g., myasthenia gravis), and myopathies. Orthopedic injuries can sometimes mimic plexopathy, usually only when symptoms are relatively mild; the examination and electrodiagnostic testing usually identifies the plexopathy. The most important mimic of plexopathy is polyradiculopathy; nerve root lesions also present with both weakness and pain. The mechanism of nerve root injury may be structural (e.g., neural foraminal stenosis or disk herniation), infectious (e.g., Lyme neuroborreliosis), or neoplastic (e.g., carcinomatous meningitis).

ANATOMY Brachial Plexus The brachial plexus is formed from the ventral rami of cervical roots 5–8 and thoracic root 1 (Fig. 64-3). The ventral rami of



CHAPTER 64  •  Brachial and Lumbosacral Plexopathies  593

A

B

Axial (A) and sagittal (B) T1-weighted post gadolinium-enhanced images of the brachial plexus showing enhancement around the right brachial plexus (arrows). Figure 64-2  Parsonage-Turner brachial plexitis.

the fifth and sixth cervical roots together form the upper trunk, the seventh cervical root ventral ramus becomes the middle trunk, and the eighth cervical and first thoracic root ventral rami join to become the lower trunk. The trunks of the brachial plexus are located above the clavicle between the scalenus anterior and scalenus medius muscles, in the posterior triangle of the neck, posterior and lateral to the sternocleidomastoid muscle. The dorsal scapular, long thoracic, and suprascapular nerves originate from the brachial plexus above the clavicle. Behind the clavicle and in front of the first rib, each trunk separates into anterior and posterior divisions. The anterior divisions of the upper and middle trunks unite to become the lateral cord, whereas the anterior division of the lower trunk forms the medial cord. The posterior divisions of all three trunks unite to become the posterior cord. The three cords are named for their positions relative to the axillary artery. Below the clavicle, the upper extremity nerves arise from the cords. From the lateral cord arises the musculocutaneous, the lateral head of the median, and the lateral pectoral nerves. From the medial cord comes the ulnar, the medial head of the median, the medial pectoral, and the medial brachial and medial antebrachial nerves. From the posterior cord arise the radial, axillary, subscapular, and thoracodorsal nerves.

Lumbosacral Plexus The femoral nerve, innervating the iliopsoas and the quadriceps femoris muscles, is the predominant derivative of the lumbar portion of the lumbosacral plexus (Fig. 64-4). Its sensory supply includes the anterior and lateral thigh, and the medial foreleg as the saphenous nerve. The obturator nerve innervating the adductor magnus also originates from the lumbar plexus. The sacral portion of the lumbosacral plexus innervates the remainder of the lower extremity muscles, including posterior thigh and buttocks muscles and all leg musculature below the knee.

The superior and inferior gluteal nerves, the most proximal nerves originating from the sacral derivative of the lumbosacral plexus, innervate the gluteal muscles (medius, minimus, and maximus). The sciatic nerve innervates the hamstring group and bifurcates into the peroneal and tibial nerves, providing all motor innervation below the knee. The sciatic nerve provides sensory innervation to the posterior thigh and the entire leg below the knee, with the exception of the medial foreleg, which is supplied only by the saphenous nerve. The peroneal nerve is derived from the lateral portion of the sciatic nerve within the thigh; it supplies only one muscle above the knee, the short head of the biceps femoris. This site provides a means to differentiate electrodiagnostically atypical proximal peroneal or sciatic nerve lesions from common peroneal nerve compression or entrapment syndromes at the fibular head. The peroneal nerve bifurcates into the superficial and deep peroneal nerves, the latter innervating all anterior compartment muscles. The superficial peroneal motor nerve supplies the lateral compartment. The tibial nerve, the other primary sciatic nerve derivative, supplies the calf. The superficial peroneal sensory, the sural, and the medial and lateral plantar nerves are the primary superficial sensory nerves below the knee, in addition to the saphenous.

DIAGNOSTIC APPROACH The neurologic examination should focus on identifying any motor, sensory, and reflex impairment referable to the different components of the plexus. A diminished or absent biceps reflex would be expected for a brachial plexopathy involving the upper trunk, for example. Weakness involving the hand and wrist would point toward lower trunk/medial cord brachial plexus involvement. In addition to localizing a lesion to particular trunks and cords, the examination can sometimes help determine whether lesions are preganglionic (e.g., root avulsion) or postganglionic (e.g., upper trunk plexopathy). Weakness of the

594  SECTION XIV  •  Radiculopathies and Plexopathies

Comparison of Embryonic Limb Organization to the Plan of the Brachial Plexus

Anterior division Posterior division

To phrenic nerve

Suprascapular nerve (C5, C6) To subclavius muscle (C5, C6)

ds

Up

Mid

Lo

L

Musculocutaneous nerve (C5, C6, C7)

r

T1

r

rio

ste

Po

C5

C8

we

l

ra

e at

Dorsal ramus

C7

dle

Lateral pectoral nerve (C5, C6, C7)

Contribution from C4

C6

per

or

al in s rm he Te anc Br

ks

run

3T

s ion vis ns Di ivisio r rio D nte rior 3 A oste 3P

3C

ots 5 Ro ami of ral R ves) t n e r (V al Ne Spin Dorsal scapular nerve (C5)

Contribution from T2 To longus colli and scalene muscles (C5, C6, C7, C8)

1st rib l

dia Me

Axillary nerve (C5, C6)

1st intercostal nerve Long thoracic nerve (C5, C6, C7) Medial pectoral nerve (C8, T1)

Radial nerve (C5, C6, C7, C8, T1)

Medial cutaneous nerve of arm (T1)

Median nerve (C5, C6, C7, C8, T1)

Medial cutaneous nerve of forearm (C8, T1) Ulnar nerve (C7, C8, T1)

Upper subscapular nerve (C5, C6) Thoracodorsal (middle subscapular) nerve (C6, C7, C8)

Inconstant contribution

Lower subscapular nerve (C5, C6)

Axilla (Dissection): Anterior View Pectoralis minor tendon (cut) Acromial branch Deltoid branch Coracoid process Clavicular branch Acromion Cephalic vein Musculocutaneous nerve Anterior circumflex humeral artery Pectoralis major muscle (cut) Deltoid muscle Axillary nerve and posterior circumflex humeral artery Coracobrachialis muscle Biceps brachii muscle

Trapezius muscle Suprascapular artery and nerve Dorsal scapular artery and nerve Sternocleidomastoid muscle Anterior scalene muscle Phrenic nerve Omohyoid muscle Transverse cervical artery Brachial plexus Subclavian artery and vein Clavicle and subclavius muscle (cut) 1st rib

Musculocutaneous nerve

Pectoral branch

Brachialis muscle

Superior thoracic artery

Deep artery of arm Axillary artery

Radial nerve Brachial veins

Ulnar nerve Medial cutaneous Triceps brachii muscle nerve of arm Ulnar nerve Intercostobrachial Median nerve nerve Brachial artery Circumflex scapular artery Medial cutaneous nerve of the forearm Lower subscapular nerve Basilic vein Teres major muscle Latissimus dorsi muscle Thoracodorsal artery and nerve

Figure 64-3  Anatomy of Brachial Plexus.

Lateral pectoral nerve Thoracoacromial artery

Medial pectoral nerve Pectoralis minor muscle (cut) Upper subscapular nerve Subscapular artery Lateral thoracic artery and long thoracic nerve Serratus anterior muscle



CHAPTER 64  •  Brachial and Lumbosacral Plexopathies  595

Lumbar Plexus Schema

Subcostal nerve (T12)

White and gray rami communicantes

T12 L1

Iliohypogastric nerve

White and gray rami communicantes

Diaphragm (cut) L2

Ilioinguinal nerve

Subcostal nerve (T12)

Subcostal nerve (T12)

Iliohypogastric nerve

Sympathetic trunk

Genitofemoral nerve L3

Lateral cutaneous nerve of thigh Gray rami communicantes

L4

Muscular branches to psoas and iliacus muscles

Iliohypogastric nerve Ventral Ilioinguinal nerve rami of Genitofemoral spinal nerve (cut) nerves Lateral cutaneous nerve of thigh

Accessory obturator nerve (often absent) Obturator nerve Lumbosacral trunk

L2

Ilioinguinal nerve Transversus abdominis muscle

L3

Quadratus lumborum muscle Psoas major muscle

L4

Gray rami communicantes Genitofemoral nerve

Femoral nerve

L5

Femoral nerve

L1

Iliacus muscle

Obturator nerve

Anterior division Posterior division

Lateral cutaneous nerve of thigh Femoral nerve

Psoas major muscle (cut) Lumbosacral trunks

Genital branch and Femoral branch of genitofemoral nerve

Inguinal ligament (Poupart)

Obturator nerve

Sacral and Coccygeal Plexuses Anterior division Posterior division

Schema

Lumbosacral trunk Superior gluteal nerve Inferior gluteal nerve Nerve to piriformis

L4 L5 S1 S2 S3

Gray rami communicantes Pelvic splanchnic nerves (parasympathetic to inferior hypogastric [pelvic] plexus)

Sciatic nerve

Common fibular (peroneal) nerve

Nerve to quadratus femoris (and inferior gemellus) Nerve to obturator internus (and superior gemellus) Posterior cutaneous nerve of thigh

S5

Gray rami communicantes

Psoas major muscle

Superior gluteal artery and nerve Obturator nerve

S4 Tibial nerve

Sympathetic trunk

Lumbosacral trunk

Iliacus muscle Inferior gluteal artery Nerve to quadratus femoris

Pelvic splanchnic nerves (cut) (parasympathetic to inferior hypogastric [pelvic] plexus)

L5 L4 S1 S2 S3

Internal pudendal artery Coccygeal nerve Nerve to obturator internus Anococcygeal nerve Pudendal nerve Perineal branch of Obturator internus muscle 4th sacral nerve Superior pubic ramus Nerve to levator ani and Piriformis muscle (ischio-)coccygeus muscles Pudendal nerve (Ischio-)coccygeus muscle Perforating cutaneous nerve Nerve to levator ani muscle Levator ani muscle Topography: medial and slightly anterior view of hemisected pelvis

S4 S5 Co

Sacral splanchnic nerves (cut) (sympathetic to inferior hypogastric [pelvic] plexus)

Figure 64-4  Anatomy of Lumbar, Sacral, and Coccygeal Plexuses.

rhomboid muscles (from C4 and C5 roots) and the serratus anterior muscle (from C5, C6, and C7 roots) would suggest involvement as proximal as the cervical root. Needle examination of these muscles and cervical paraspinal muscles, discussed below, will be helpful also in determining where the lesions are along the length of the nerve. Electrodiagnostic (EDX) testing helps confirm the diagnosis and localization of a suspected plexopathy. Rarely, nonneuropathic processes (e.g., rotator cuff tendinitis, hip fracture) can mimic plexopathy, in which case EDX testing and the neurologic examination will be normal. More commonly, EDX testing serves to confirm localization of a neuropathic process to the

plexus. A watershed for the localization of plexopathies is the dorsal root ganglia (DRG), with lesions involving segments proximal to the DRG (e.g., root) classified as preganglionic lesions, whereas those distal to the DRG (e.g., trunk) are labeled as postganglionic lesions. Assessment of sensory nerve action potentials (SNAPs) is very helpful with this localization because the preservation of SNAPs favors a preganglionic lesion (e.g., radiculopathy) whereas the diminution or loss of SNAPs favors a postganglionic lesion (e.g., plexopathy). For a unilateral plexopathy, the SNAP abnormality should be on the side of the lesion, and for asymmetric plexopathies, the SNAP abnormalities should theoretically be more severe on the more affected

596  SECTION XIV  •  Radiculopathies and Plexopathies

side. Side-to-side differences in SNAP amplitude of greater than 50% are typically considered significant, but repeat testing at the same sitting to confirm that this finding is not simply technical is advisable, particularly given the significance of such a finding for localization. Differentiating preganglionic (e.g., radiculopathy) from postganglionic plexopathy is a particularly important request when trying to differentiate a structural (e.g., spinal stenosis), infectious (e.g., Lyme), or carcinomatous cervical polyradiculopathy from a plexopathy. Determining whether a traumatic plexus injury is preganglionic or postganglionic is also important for surgical management. For instance, preganglionic lesions (e.g., root avulsions) are generally not amenable to direct plexus repair with nerve grafting and hence would more likely be surgically treated with a nerve transfer (e.g., spinal accessory nerve to suprascapular nerve in order to allow shoulder abduction, ulnar nerve fascicle to flexor carpi ulnaris to the musculocutaneous nerve in order to allow elbow flexion). On the other hand, postganglionic lesions (e.g., upper trunk plexopathy) may be directly repaired at the plexus with nerve grafting or internal neurolysis. In the case presented above, the absent sural sensory and superficial peroneal sensory responses were consistent with a postganglionic plexopathy. Motor nerve conduction studies should also be performed, particularly to look for low CMAP amplitudes over muscles innervated by affected nerves. Needle examination helps localize the lesion, both longitudinally (i.e., where along the length of the nerve or root) and specifically to which components of the plexus (e.g., upper trunk). Needle examination should ideally be performed at least 2–3 weeks after onset in order to maximize what data can be collected from the study, but it still can be helpful to perform a study earlier than that because reduced recruitment of motor unit potentials of weak muscles can still help with localization. Abnormalities on needle examination can map out the location of the plexus lesions. The presence of fibrillation potentials in paraspinal muscles would point to involvement of the roots; however, the absence of fibrillation potentials in the paraspinals does not exclude radiculopathy because needle examination of paraspinal muscles will be normal in an estimated half of patients with radiculopathy. It is important to also note that patients with radiculoplexus neuropathies (e.g., DLRPN) will demonstrate evidence of both preganglionic and postganglionic damage, hence the name radiculoplexus neuropathy. Needle examination can also sometimes assist in determining etiology. For example, plexopathies secondary to radiotherapy are sometimes associated with myokymic discharges on needle study, whereas plexopathies due to another cause (e.g., neoplasm) are much less likely to reveal myokymic discharges. Routine radiographs, CT, and MRI of the lumbosacral spine and pelvis are often required to exclude inflammatory or mass lesions within the spine or pelvis. CSF examination may be indicated to exclude infection. CSF protein is increased in approximately 50% of patients with idiopathic lumbosacral plexopathy. In vasculitic lumbosacral plexopathy, nerve biopsy may reveal ischemic nerve injury caused by microvasculitis or vasculitis. Histopathologic evidence of vasculitis is frequently seen on biopsy of patients with DLRPN, although often the clinical context and other ancillary studies provide enough evidence of the diagnosis so that a nerve biopsy can be avoided.

DIFFERENTIAL DIAGNOSIS Trauma is the most common pathophysiologic mechanism for a brachial plexopathy. The superficial anatomic location of the brachial plexus with close proximity to bony and vascular structures within the shoulder and neck predisposes it to this risk. Traumatic mechanisms for brachial plexopathy include compression, traction, ischemia, laceration, or a combination. Motor vehicle accidents, high-speed cycling accidents, gunshot or knife wounds, and falls can be causative. Some events may be iatrogenic; for example, positioning during cardiothoracic surgery that maximally abducts the arm, may cause stretching of the lateral brachial plexus. Sporting activities causing “burners” or “stingers” are common mechanisms for brachial plexopathy. Despite their relative frequency, their pathophysiology is unclear; these injuries are likely caused by compression, traction or both, usually of the C5–6 cervical nerve roots and upper trunk of the brachial plexus. Trauma to the lumbosacral plexus, on the other hand, is uncommon because the nerves are relatively immobile and protected by the vertebrae, psoas muscle, and pelvis. Most traumatic injuries are associated with pelvic or acetabular fractures, frequently with soft-tissue injuries to other pelvic organs. Neuralgic amyotrophy (also known as idiopathic brachial plexus neuropathy or Parsonage–Turner syndrome) and diabetic lumbosacral radiculoplexus neuropathy (DLRPN; also known as diabetic amyotrophy) are thought to be autoimmune in origin. Both conditions are likely caused by microvasculitis, in which case the autoimmune attack is directed at small vessels within and near the nerves of the roots, plexus and proximal nerves. Neuralgic amyotrophy of the brachial plexus sometimes occurs after a viral illness, vaccination, or mild trauma or during the immediate postpartum period. Usually, these patients present with relatively acute shoulder pain and partial loss of brachial plexus function. Typically, neuralgic amyotrophy predominantly affects nerves of the shoulder girdle muscles, although other portions of the plexus and its terminal branches are occasionally involved, especially the anterior interosseous segment of the median nerve. Approximately one third of patients with neuralgic amyotrophy have bilateral, asymmetric involvement. DLRPN is the most common cause of lumbosacral plexopathy (Fig. 64-5). DLRPN typically presents in older patients who have type 2 diabetes mellitus, with abrupt or subacute onset of hip and thigh severe pain (see case presentation above). Weakness and muscle atrophy occur within a week or two, often at the time the pain begins to improve. Muscle stretch reflexes may be lost, especially at the knee. DLRPN often begins unilaterally but frequently progresses to bilateral involvement. This monophasic disorder is usually significantly disabling and is commonly associated with unexplained weight loss. Like neuralgic amyotrophy, DLRPN is thought to originate from peripheral nerve microvasculitis. Idiopathic lumbosacral radiculoplexus neuropathy (LRPN) is a rare primary plexopathy that occurs in nondiabetics. It is also manifested by rapid onset of pain, leg weakness, and atrophy. Patients often experience a viral illness 1–2 weeks before symptoms begin. Lumbar plexus involvement often affects the most proximal musculature, causing weakness of the iliopsoas, quadriceps, and adductor muscles. Often, significant recovery occurs within 3 months.



CHAPTER 64  •  Brachial and Lumbosacral Plexopathies  597

Diabetic Radiculopathy

Lumbosacral Plexopathy Possible site of lesion: roots of spinal nerve at emergence from spinal canal or proximal plexus

Femoral adiculopathy: pain in thigh

Lymphoma compressing lumbar plexus Iliohypogastric n. Ilioinguinal n.

Pain in femoral region From T7 L1

Genitofemoral n.

L2

Lateral femoral cutaneous n.

L3 L4

Femoral n.

L5

Lumbosacral trunk

Hematoma compressing sacral plexus

From L4

Pain in back of thigh

L5 Superior gluteal n. S1 Loss of knee jerk (often unilateral)

Inferior gluteal n. S2 Sciatic n.

Thoracic radiculopathy: woman unfastens brassiere—cannot tolerate tightness because of hyperesthesia and pain in thoracic region

S3 S4

Posterior femoral cutaneous n. Pudendal n.

Figure 64-5  Causes of Lumbosacral Radiculoplexopathies.

Hereditary neuralgic amyotrophy (also known as hereditary brachial plexus neuropathy) is an autosomal dominant disorder characterized by periodic, often recurrent, episodes of unilateral or asymmetric pain, weakness, atrophy, and sensory alterations in the shoulder girdle and upper extremity. Genetically, many cases of HBPN are caused by mutations in the SEPT9 gene. Hereditary neuralgic amyotrophy is also believed to be an immune-mediated disorder and likely a microvasculitis with a strong genetic predisposition caused by an inherited SEPT9 mutation. Malignant tumors, particularly apical lung or postradiation breast cancer, are common causes of brachial plexus lesions (Fig. 64-6). With apical lung tumors, the lesion may insidiously advance, causing numbness in the fourth and fifth fingers, weakness in the ulnar and median hand intrinsic muscles, and Horner syndrome (Pancoast tumor). Often, pain is significant, secondary to neoplastic infiltration of the brachial plexus. This clinical constellation sometimes precedes recognition of the lung tumor. Every patient who smokes and presents in this fashion requires a chest CT or MRI. Tumors occasionally invade the lumbosacral plexus by primary extension from pelvic, abdominal, or retroperitoneal malignancies (see Fig. 64-5). Pain in the distribution of the affected nerves is the cardinal symptom. Late symptoms and signs may include numbness and paresthesias, weakness and gait abnormalities, and lower extremity edema. Retroperitoneal

Coronal T1-weighted image demonstrates large left apical lung mass extending into brachial plexus (arrows). Figure 64-6  Apical lung tumor invading left brachial plexus.

598  SECTION XIV  •  Radiculopathies and Plexopathies

TREATMENT AND PROGNOSIS Treatment of plexus lesions comprises management of the primary condition. Careful glucose control may hasten DLRPN recovery and improve outcome. The efficacy of steroids or intravenous immunoglobulin in the acute or subacute phase of DLRPN is not proven, although anecdotal reports suggest clinical benefit and some evidence is emerging that the pain and other neuropathic symptoms may respond to these treatment options. Most traumatic lesions are treated conservatively, although pelvic fractures and gunshot wounds may necessitate surgery. No effective treatment exists for radiation-induced brachial or lumbosacral plexopathy. Oncologic intervention is necessary for neoplastic brachial or lumbosacral plexopathy. Symptomatic pain management is usually necessary. Pain control with narcotics is often necessary in the acute phase of DLRPN, LRPN, neuralgic amyotrophy, hereditary neuralgic amyotrophy, traumatic plexopathy, and neoplastic plexopathies. Figure 64-7  Large hematoma involves the left iliacus and psoas muscles (arrow) and adjacent region, likely involving the lumbar plexus and femoral nerve.

hematomas can compress the lumbar or sacral plexuses or both. Patients present with unilateral pelvic or groin pain; the patient preferentially has the hip flexed to minimize pressure on the plexus (Fig. 64-7). This condition is typically a comp­ lication of anticoagulation therapy, or less commonly bleeding diatheses, and immediate surgical decompression can be beneficial. Compressive lumbosacral plexopathies may also occur from a number of other mechanisms, including late pregnancy or childbirth and abdominal aortic aneurysms. A retroperitoneal infection such as a psoas abscess rarely affects the lumbosacral plexus. Radiation-induced lumbosacral plexopathies develop months to years after radiotherapy to pelvic malignancies. The lumbar plexus is more commonly affected in radiation-induced lesions, whereas the sacral plexus is more frequently affected by neoplastic plexopathies. Painless weakness develops at a variable rate, ultimately causing asymmetric but significant weakness of both lower extremities. Paresthesias and pain are common but usually mild. Sphincter involvement is rare.

ADDITIONAL RESOURCES Dyck PJ, Norell JE, Dyck PJ. Microvasculitis and ischemia in diabetic lumbosacral radiculoplexus neuropathy. Neurology 1999;53:2113-2121. Dyck PJ, Norell JE, Dyck PJ. Non-diabetic lumbosacral radiculoplexus neuropathy: natural history, outcome and comparison with the diabetic variety. Brain 2001;124:1197-1207. Ferrante MA. Brachial plexopathies: classification, causes, and consequences. Muscle Nerve 2004;30:547-568. Lederman RJ, Wilbourn AJ. Postpartum neuralgic amyotrophy. Neurology 1996;47:1213-1219. Moghekar AR, Moghekar AB, Karli N, et al. Brachial plexopathies. Etiology, frequency and electrodiagnostic localization. J Clin Neuromusc Dis 2007;9:243-247. Parsonage MJ, Turner JWA. Neuralgic amyotrophy. The shoulder-girdle syndrome. Lancet 1948;973-978. Rubin DI. Diseases of the plexus. Continuum 2008;14:156-181. Suarez GA, Giannini C, Bosch EP, et al. Immune brachial plexus neuropathy: suggestive evidence for an inflammatory immune pathogenesis. Neurology 1996;46:559-561. Triggs W, Young MS, Eskin T, et al. Treatment of idiopathic lumbosacral plexopathy with intravenous immunoglobulin. Muscle Nerve 1997;20: 244-246. Tsairis P, Dyck PJ, Mulder DW. Natural history of brachial plexus neuropathy. Report on 99 patients. Arch Neurol 1972;27:109-117. Van Alfen N. The neuralgic amyotrophy consultation. J Neurol 2007;254: 695-704. Van Alfen N, van Engelen BGM. The clinical spectrum of neuralgic amyotrophy in 246 cases. Brain 2006;129:438-450. Verma A, Bradley WB. High dose intravenous immunoglobulin therapy in chronic progressive lumbosacral plexopathy. Neurology 1994;44: 248-250.

Mononeuropathies of the Upper Extremities

65 

Gisela Held and Miruna Segarceanu

MONONEUROPATHIES OF THE SHOULDER GIRDLE Mononeuropathies of the shoulder girdle are relatively uncommon and can be challenging to diagnose. Unlike other mononeuropathies, pain is often the cardinal symptom, and shoulder pain and weakness, real or perceived, can originate from mononeuropathies, but also from cervical disc disease, disorders of the musculoskeletal system, or vascular causes. True weakness can be difficult to separate from impaired effort due to pain. Shoulder muscles might appear weak in rotator cuff or other tendon tears in the absence of nerve injury. Shoulder girdle mononeuropathies are caused by the following mechanisms: stretch, transecting injury, brachial plexus neuritis with patchy involvement of isolated nerves, direct compression, or entrapment. The history should help define the precise location of the pain, positions and activities that provoke pain, the time of day of maximal discomfort, and any precipitating injury. Paresthesias or sensory loss, particularly if well defined within a recognized single nerve distribution, usually indicates peripheral nerve pathology. Atrophy can be related to axon loss or occasionally prolonged disuse; sometimes the clinical distinction is difficult. Shoulder motion is evaluated for abnormal dynamics of the glenohumeral, acromioclavicular, and scapulothoracic joints.

DORSAL SCAPULAR NEUROPATHIES

Clinical Vignette A 27-year-old professional weight lifter complained about difficulty exercising. He had trouble getting his wallet out of the right back pocket of his pants. Examination revealed weakness of the right rhomboid muscles without noticeable muscle atrophy. There was scapular winging with lateral displacement of the scapula, most pronounced during elevation of the arm. Electrophysiologic testing disclosed active and chronic denervation–reinnervation changes in the right rhomboids. Testing of other arm and shoulder muscles was normal.

The dorsal scapular nerve receives fibers from the C5 nerve root. It innervates the levator scapulae and the rhomboideus major and minor muscles, which assist in stabilization of the scapula, rotation of the scapula in a medial–inferior direction, and elevation of the arm (Fig. 65-1). Rhomboid weakness can lead to scapular winging, which is most prominent when the patient raises the arm overhead. Possible etiologies of injury to

this nerve include shoulder dislocation, weightlifting, and entrapment by the scalenus medius muscle.

LONG THORACIC NEUROPATHIES Clinical Vignette A 57-year-old left-handed woman underwent a left mastectomy for breast cancer. Immediately following the surgery, she noted an aching pain in the left posterior shoulder area. After discharge from the hospital, she had difficulty using the left arm. In particular, she complained of being unable to get dishes from the kitchen cabinets. She was not aware of sensory loss. Electrodiagnostic testing 3 weeks later showed evidence of acute denervation changes in the left serratus anterior muscle, consistent with a mononeuropathy of the long thoracic nerve.

The long thoracic nerve originates directly from C5–C7 roots, before the formation of the brachial plexus. It innervates the serratus anterior muscle and has no cutaneous sensory representation (Fig. 65-2). Weakness of the serratus anterior is debilitating, because it stabilizes the scapula for pushing movements and elevates the arm above 90 degrees. This is the most common cause of scapular winging; it is best recognized by having the patient push against a wall. The inferior medial border is the most prominently projected away from the body wall. A dull shoulder ache may accompany this neuropathy. When severe acute pain occurs with the onset of scapular winging, brachial plexus neuritis should be considered. The long thoracic nerve may be damaged by mechanical factors, including repetitive or particularly forceful injuries to the shoulder or lateral thoracic wall and by surgical procedures including first rib resection, mastectomy, or thoracotomy. It is one of the most common nerves to be affected by acute brachial neuritis, solely or in combination with others. Scapular winging can also be related to scapular fracture and avulsion. Because they are surgically correctable, it is important to distinguish them from a primary long thoracic nerve injury. Furthermore, scapular winging can be caused by weakness of the trapezius (resulting from injury of the spinal accessory nerve) or the rhomboid muscles (resulting from a dorsal scapular nerve lesion). Inspection of the posterior shoulder region can provide diagnostic clues. Although the scapula is typically displaced medially in long thoracic nerve lesions, lateral deviation points to weakness of the trapezius or rhomboids. Scapular winging is a predominant feature in patients with facioscapulohumeral muscular dystrophy, where its bilateral representation and the other associated clinical features distinguish it from long thoracic nerve palsy.



CHAPTER 65  •  Mononeuropathies of the Upper Extremities  601

Dorsal scapular nerve (C5)

Posterior view

Supraspinatus muscle Suprascapular nerve (C5, 6)

Levator scapulae muscle (supplied also by branches from C3 and C4)

Deltoid muscle Teres minor muscle Axillary nerve (C5, 6)

Rhomboid minor muscle Radial nerve (C5, 6, 7, 8, T1)

Rhomboid major muscle

Inferior lateral cutaneous nerve of arm Posterior cutaneous nerve of forearm

Infraspinatus muscle Teres major muscle Lower subscapular nerve (C5, 6) Posterior brachial cutaneous nerve of arm (branch of radial nerve in axilla) Long head Triceps brachii muscle Lateral head Medial head Triceps brachii tendon

Lateral intermuscular septum Brachialis muscle (lateral part; remainder of muscle supplied by musculocutaneous nerve) Brachioradialis muscle

Olecranon Anconeus muscle

Figure 65-1  Radial Nerve in Arm and Nerves of Posterior Shoulder.

SUPRASCAPULAR NEUROPATHIES Clinical Vignette A 25-year-old right-handed woman was evaluated for dull right shoulder pain and weakness. The symptoms were most noticeable during overhead activities. She had no sensory loss, and no injury had preceded the onset of her symptoms. Examination disclosed tenderness to palpation at the spinoglenoid notch. Shoulder position was normal; range of motion was full. Motor examination was significant for weakness of external shoulder rotation and mild atrophy of the infraspinatus muscle overlying the scapula. Reflexes and sensory examination were normal. These findings of infraspinatus atrophy, weak external rotation of the shoulder, and point tenderness over the spinoglenoid notch were consistent with a focal suprascapular neuropathy. Electromyography (EMG) demonstrated active denervation changes confined to the infraspinatus muscle consistent with the clinical diagnosis. A magnetic resonance image (MRI) of the right shoulder revealed a cystic lesion at the spinoglenoid notch, which was confirmed by surgical exploration.

shoulder abductor, and then to the infraspinatus, a shoulder external rotator (see Fig. 65-1). The suprascapular nerve may be injured at the suprascapular notch, before the innervation of the supraspinatus muscle, or distally at the spinoglenoid notch, affecting the infraspinatus alone (see Fig. 65-2). The most common site of entrapment is at the suprascapular notch, under the transverse scapular ligament. Acute-onset cases result from blunt shoulder trauma, with or without scapular fracture, or from forceful anterior rotation of the scapula. The suprascapular nerve may also be affected by brachial plexus neuritis in isolation or with other nerves. Suprascapular neuropathies of insidious onset often occur subsequent to callous formation after fractures, from entrapment at the suprascapular or spinoglenoid notch, by com­pression from a ganglion or other soft tissue mass, or by traction caused by repetitive overhead activities such as volleyball or tennis.

AXILLARY NEUROPATHIES Clinical Vignette A 72-year-old man had pain and weakness of the right arm following a fall. Evaluation in the emergency room disclosed an anterior dislocation of the right shoulder, which was reduced. Despite treatment, the patient continued to have difficulty raising the arm above the head. Electrodiagnostic testing several weeks later showed reduced recruitment pattern of motor unit action potentials in the right deltoid and teres minor muscles. The EMG was suggestive of stretch injury with demyelinating nerve injury without evidence of axon loss. The patient recovered spontaneously over the course of the following month.

The axillary nerve, along with the radial nerve, is a terminal branch of the posterior cord of the brachial plexus. It innervates the deltoid and the teres minor and provides sensory innervation to the lateral upper part of the shoulder via the superior lateral brachial cutaneous nerve of the arm (Figs. 65-1 and 65-3). In lesions of the axillary nerve, shoulder abduction is weakened and cutaneous sensibility of the lateral shoulder diminishes, overlapping the C5 dermatome. Because the teres minor is not the predominant external rotator of the shoulder, clinical isolation and testing are difficult. EMG may be necessary to define neurogenic injury to this muscle. Most axillary neuropathies are traumatic, related to anterior shoulder dislocations, humerus fractures, or both. Recognition of nerve injury may be delayed because of the shoulder injury. Acute axillary neuropathies can result from blunt trauma or as a component or sole manifestation of brachial plexus neuritis.

MUSCULOCUTANEOUS NEUROPATHIES Clinical Vignette

The suprascapular nerve emerges from the upper trunk of the brachial plexus, receiving fibers from C5 and C6 roots. It does not have any cutaneous innervation. The suprascapular nerve first provides innervation to the supraspinatus muscle, a

A 43-year-old woman presented to the laboratory for routine blood work after her annual physical examination. During phlebotomy in the right antecubital fossa, she experienced

602  SECTION XV  •  Mononeuropathies

Suprascapular Nerve Supraspinatus m. Suprascapular n. in suprascapular notch Pain radiation Pain

Infraspinatus m. Axillary n.

Compression of suprascapular nerve may cause lateral shoulder pain and atrophy of supraspinatus and infraspinatus muscles.

Musculocutaneous Nerve Musculocutaneous nerve compression within coracobrachialis muscle causes hypesthesia in lateral forearm and weakness of elbow flexion.

Coracobrachialis m.

Weakness of elbow flexion Hypesthesia

Musculocutaneous n. Biceps brachii m. Brachialis m.

Long Thoracic Nerve Compression of long thoracic nerve causes paresis of serratus anterior muscle and winging of scapula. Winging of scapula

Serratus anterior m. (helps stabilize scapula) Long thoracic n.

Normal

Figure 65-2  Neuropathy about Shoulder. a sharp pain, radiating from the elbow to the wrist, which persisted for several days. She then developed numbness of the right lateral forearm. She had no weakness. Nerve conduction studies showed an absent sensory nerve action potential of the lateral antebrachial cutaneous nerve. The needle examination was normal.

The musculocutaneous nerve originates directly from the lateral cord of the brachial plexus. It innervates the coracobrachialis, biceps brachii, and brachialis muscles and terminates in its cutaneous branch, the lateral antebrachial cutaneous nerve. Isolated musculocutaneous neuropathies are rare. They have

been reported in weight lifters, after surgery, and after prolonged pressure during sleep. Damage to the musculocutaneous nerve results in weakness of forearm flexion and supination and sensory loss of the lateral volar forearm (see Fig. 65-2). The biceps reflex is diminished, but the brachioradialis reflex (same myotome, different nerve) is preserved. More commonly, injury to this nerve occurs as part of a more widespread traumatic injury, usually involving the proximal humerus. The musculocutaneous nerve can also be preferentially involved in acute brachial plexus neuritis. Distal lesions of the lateral antebrachial cutaneous nerve may result from attempted cannulation of the basilic vein in the antecubital fossa. Rupture of the biceps tendon is a significant differential diagnostic consideration of musculocutaneous neuropathy.



CHAPTER 65  •  Mononeuropathies of the Upper Extremities  603

Anterior (palmar) view

Posterior (dorsal) view

Supraclavicular nerves (from cervical plexus – C3, 4)

Supraclavicular nerves (from cervical plexus – C3, 4) Axillary nerve Superior lateral cutaneous nerve of arm (C5, 6)

Axillary nerve Superior lateral cutaneous nerve of arm (C5, 6)

Radial nerve Inferior lateral cutaneous nerve of arm (C5, 6)

Intercostobrachial nerve (T2) and medial cutaneous nerve of arm (C8, T1, 2) Lateral cutaneous nerve of forearm (C5, 6 [7]) (terminal part of musculocutaneous nerve)

Medial cutaneous nerve of forearm (C8, T1)

Radial nerve Posterior cutaneous nerve of arm (C5, 6, 7, 8) Inferior lateral cutaneous nerve of arm Posterior cutaneous nerve of forearm (C[5], 6, 7, 8)

Lateral cutaneous nerve of forearm (C5, 6, [7]) (terminal part of musculocutaneous nerve)

Ulnar nerve (C8, T1) Radial nerve Superficial branch (C6, 7, 8)

Palmar branch Palmar digital branches

Median nerve Palmar branch and Palmar digital branches (C6, 7, 8)

Dorsal branch and dorsal digital branches Proper palmar digital branches

Note: Division is variable between ulnar and radial innervation on dorsum of hand and often aligns with middle of 3rd digit instead of 4th digit as shown.

Radial nerve Superficial branch and dorsal digital branches (C6, 7, 8)

Median nerve Proper palmar digital branches

Figure 65-3  Cutaneous Innervation of the Upper Limb.

DIFFERENTIAL DIAGNOSIS The most common etiologies of shoulder pain are injuries to glenohumeral, subacromial, and acromioclavicular regions. Pain often may be reproduced by local pressure or provocative movements and positions. Rotator cuff tears can mimic nerve injury because of apparent weakness of shoulder abduction (supraspinatus) and external rotation (teres minor and infraspinatus). Motor neuron disease may begin in the shoulder region. It must be considered in the differential diagnosis of weakness without associated pain or sensory signs and symptoms. C5 radiculopathy also enters the differential diagnosis in patients reporting shoulder pain sometimes extending into the upper arm with weakness and numbness. This pain might originate within the scapular region and not the neck. Having patients flex their neck laterally in the direction of the symptomatic limb may reproduce the pain. Patients with C5 weakness have problems with shoulder abduction (deltoid and supraspinatus muscles), external rotation (infraspinatus), and arm flexion (biceps brachii). The biceps stretch reflex is often diminished. Paresthesias or sensory loss occurs in a discrete patch on the lateral proximal arm overlying the deltoid muscle.

DIAGNOSTIC APPROACH EMG is the primary diagnostic tool in the evaluation of suspected shoulder mononeuropathies. It is particularly helpful

to identify mononeuropathies affecting the shoulder girdle for several reasons. Neurogenic injury may go unsuspected because pain is the predominant symptom. Weakness may be hidden by the observation of normal strength within unaffected muscles performing similar functions, for example, supraspinatus weakness obscured by normal deltoid function. Conversely, nerve injury may be suspected because of apparent weakness caused by tendon rupture, only to be refuted by the absence of denervation on needle EMG. Although theoretically nerve conduction studies can be performed on the musculocutaneous and axillary nerves, their value is limited by technical factors. These nerves are typically accessible at only one stimulation site, precluding the determination of conduction velocities and accurate identification of conduction block. However, demyelination with conduction block may be suspected when a normal compound muscle action potential is obtained from a weak muscle; often, this finding portends an excellent prognosis. This conclusion should be reached cautiously because the same pattern may result from axon loss when the study is performed within the first week after injury, before wallerian degeneration has taken place. Needle EMG can identify even subtle axon loss by the detection of fibrillation potentials. The evaluating physician and the electromyographer should always examine the patient and consider every potential neuropathic cause of shoulder pain. Other­ wise, uncommon neuropathies can easily be overlooked.

604  SECTION XV  •  Mononeuropathies

A common clinical dilemma occurs with patients who have nontraumatic shoulder girdle mononeuropathies. It is difficult to differentiate a primary idiopathic lesion from a limited form of brachial plexus neuritis and to determine whether entrapment or a related process necessitating surgical exploration is involved. A thorough clinical and electrodiagnostic examination is thus required. Subtle clinical or electrodiagnostic evidence of involvement of muscles innervated by a different nerve usually suggests that a conservative approach is indicated, as this constellation of findings speaks against compression of a single nerve. Routine radiographs are useful to detect scapular fractures secondary to acute injuries, which sometimes predispose patients to suprascapular neuropathies or serratus anterior dehiscence from the scapula. MRI can define insidious-onset neuropathies that may be caused by expanding masses, for example, a ganglion cyst in the spinoglenoid notch.

MANAGEMENT AND PROGNOSIS Unfortunately, shoulder bracing provides little benefit to patients with shoulder girdle weakness. Exercises to strengthen other shoulder girdle muscles may provide partial functional compensation. If nerve transection from acute penetrating injury is suspected, surgical exploration and primary anastomosis should be considered, although results are mixed. In acute nonpenetrating injury, exploration can be considered after 3–6 months, provided no clinical or electrodiagnostic evidence of reinnervation exists. Nerve grafting is an option if unanticipated nerve transection is found. For insidious-onset neuropathies without defined cause, imaging should be considered to exclude ganglion cysts or other masses. If no mass is demonstrable and the patient shows no evidence of improvement, exploration may be considered, particularly at potential sites of entrapment such as the suprascapular or spinoglenoid notches. Despite apparent axonal injury in brachial plexus neuritis, there is a good prognosis for functional recovery. Unfortunately, this recovery typically takes 6 months to 2 years. The prognosis for direct compressive injury is less predictable and probably depends on reinnervating distance, patient age, and attendant comorbidities. Stretch injuries and entrapment have the highest likelihood of a significant demyelinating component, with excellent outcome being the rule, particularly if entrapment is recognized and removed before significant axon loss occurs.

Anterior view

Medial Cords of Posterior brachial Lateral plexus Median nerve (C6, 7, 8, T1) Radial nerve Articular branch Flexor carpi radialis muscle

Ulnar nerve

Palmaris longus muscle Pronator teres muscles (humeral head)

Pronator teres muscle (ulnar head) Flexor digitorum superficialis muscle (turned up) Flexor digitorum profundus muscle (lateral part supplied by median [anterior interosseous] nerve; medial part supplied by ulnar nerve)

Cutaneous innervation

Anterior interosseous nerve Flexor pollicis longus muscle Pronator quadratus muscle

Palmar view

Palmar branch of median nerve Thenar Abductor pollicis brevis muscles Opponens pollicis Flexor pollicis brevis 1st and 2nd lumbrical muscles

Dorsal branches to dorsum of middle and distal phalanges

Common palmar digital nerves Proper palmar digital nerves

Posterior (dorsal) view

Figure 65-4  Median Nerve.

The median nerve is formed by lateral and medial cord fibers of the brachial plexus. The lateral cord carries mainly sensory fibers from C6–C7 roots and provides the sensory innervation to the thumb and the first two and a half fingers. It also contains motor fibers from the C6-C7 roots, which contribute to the innervation of the forearm muscles. The medial cord carries motor fibers from the C8-T1 roots that innervate the thenar eminence. The distal median nerve at the wrist is the primary site of clinical involvement in carpal tunnel syndrome. More proximal lesions at the elbow are far less common.

DISTAL MEDIAN ENTRAPMENT

MEDIAN MONONEUROPATHIES The anatomy of the median nerve is important in understanding the signs and symptoms of entrapment lesions at the level of the wrist, versus the more proximal lesions. The median nerve provides essential motor and sensory function to the lateral aspect of the hand (Fig. 65-4). It supplies the intrinsic hand muscles of most of the thenar eminence and innervates several forearm muscles. Its major sensory role is to provide innervation for the thumb, index, and middle fingers and the lateral half of the ring finger.

Clinical Vignette A 45-year-old factory worker presented with a 3-year history of intermittent right hand tingling. Initially, this had occurred only in the morning on awakening. In recent months, his symptoms had awoken him at night, interfering with his sleep. He reported that “all” digits were affected and that the paresthesias were sometimes accompanied by aching of the wrist and forearm. Shaking of the hand relieved the discomfort. There was no decline of hand



CHAPTER 65  •  Mononeuropathies of the Upper Extremities  605

strength. Neurologic examination disclosed minimal weakness of right thumb abduction without loss of thenar eminence bulk. Results of reflex and sensory examinations were normal, including 2-point discrimination and graded monofilament touch. The symptoms were reproduced by nerve percussion over the median nerve at the wrist (Tinel sign).

Etiology and Epidemiology Carpal tunnel syndrome (CTS) is common and associated with high economic costs. The lifetime risk of acquiring CTS might be as high as 10%, with an approximate annual incidence of 0.3% and a peak in the 6th decade. CTS is more than three times more prevalent in women than in men and often affects both hands. The incidence is substantially increased in the working population, particularly blue-collar workers. Carpal tunnel syndrome has been associated with numerous other conditions, such as pregnancy, endocrine disorders (hypothyroidism, acromegaly, diabetes), rheumatoid arthritis, sarcoid, hemodialysis, and amyloidosis. However, most of the cases are idiopathic, related to repeated stress to the nerve, followed by edema, ischemia, and demyelination of the median nerve at the wrist. If the trauma is severe or prolonged enough, axonal loss ensues.

Clinical Presentation and Testing Median nerve entrapment at the wrist commonly presents with intermittent symptoms, including pain and paresthesias in the hand and forearm. The symptoms tend to occur on awakening or at night, and they are often provoked by certain postures or activities such as reading or driving (Fig. 65-5). The perception that paresthesias may affect all digits (rather than just the lateral three and a half innervated by the median nerve) is likely related to the greater cortical representation of the thumb and first two fingers. As CTS progresses, persistent numbness ensues, alerting the patient that the precise sensory distribution involves the volar surface of the first three and a half digits. The neurologic examination, particularly in mild CTS cases, may offer few clues. It is helpful in severe cases, in which atrophy of the thenar eminence is common. Median hand functions, primarily thumb abduction and opposition, are weak. Having the patient supinate the forearm so the palm is flat, and then raise the thumb vertically against resistance, tests the abductor pollicis brevis muscle. Forearm muscles supplied by the median nerve proximal to the flexor retinaculum are spared in CTS. Provocative tests offer supportive but not diagnostic evidence in suspected CTS (Fig. 65-6). A positive Tinel sign consists of an electric, shooting sensation (not just local discomfort) radiating into the appropriate digits with wrist percussion. Tinel and Phalen maneuvers (reproduction of paresthesias on forceful flexion of the wrist) should be performed with nonleading questions to improve response credibility. It is recommended that the Phalen maneuver be maintained for at least 1 minute before determining that the result is negative. The pressure test may be the most reliable of the three maneuvers; pressure is placed over the carpal tunnel (proximal palm, not wrist) for

20–30 seconds, attempting to reproduce paresthesias in a median nerve distribution.

Differential Diagnosis Diagnosis of CTS is usually straightforward, although other conditions may mimic CTS. The assessment of the patient needs to incorporate clinical and electrophysiologic data, as more than 10% of the asymptomatic general population might have abnormal nerve conduction parameters suggestive of CTS. The most common differential diagnosis is a C6–C7 radiculopathy, in which numbness occurs in a similar distribution, that is, digits 1 through 3. Patients with a radiculopathy usually have neck or radicular pain. Nerve conduction studies and needle EMG can differentiate these entities. Although the muscles of both thenar and hypothenar eminence originate from the C8 root, its sensory territory is confined to the medial aspect of the hand and arm. The C8 root also innervates the flexor digitorum profundus of digits 4 and 5 and the extensor indicis proprius muscles via the ulnar and radial nerves, respectively. Ulnar neuropathies have an entirely different pattern of motor and sensory loss. Carpal tunnel syndrome virtually never presents with predominant motor symptoms. If thumb abduction is weak, evidence of other motor involvement should be sought to confirm a different lesion. Weakness and atrophy confined to the median forearm muscles suggest a proximal median nerve lesion, particularly at the elbow (pronator syndrome). If more widespread weakness is demonstrated, with the absence of sensory signs or symptoms, motor neuron diseases or multifocal motor neuropathy require diagnostic consideration. A more widespread polyneuropathy should be excluded. This can occur particularly in patients with diabetes, who may not be as aware of sensory loss in their feet compared with their hands. Clinical examination and EMG usually clarify this issue. Plexopathies typically produce motor and sensory dysfunction within multiple nerve distributions in a single extremity and pain in the shoulder region. They rarely enter the CTS differential diagnosis. Although it is uncommon for CNS disorders to produce sensory signs and symptoms within the distribution of a single peripheral nerve, occasionally cervical spinal cord lesions, such as cervical spinal stenosis or intrinsic cord tumors, and very rarely focal frontoparietal brain lesions, may mimic CTS. Vitamin B12 deficiency and syringomyelia are considerations in patients with bilateral hand numbness.

Management Data regarding the natural history of CTS is scarce. Twenty to 30% of hands appear to improve spontaneously over 1–2 years, but this might in part be due to lifestyle changes, and long-term follow-up is not available. There are few randomized controlled trials comparing different treatment modalities. Treatment recommendations are further complicated by conflicting data as to whether clinical features or electrophysiological parameters can predict treatment outcome. Conservative therapies should be considered first, as carpal tunnel release surgery carries a risk of potentially serious complications, such as reflex sympathetic dystrophy (complex regional pain syndrome), injury to the median palmar cutaneous

606  SECTION XV  •  Mononeuropathies

Patient awakened by tingling and/or pain in thumb, index, and middle fingers

Atrophy of thenar muscles due to long-standing compression of median nerve Median n.

Transverse carpal ligament

Palmar cutaneous branch of median n. Thenar mm. Abductor pollicis brevis

Carpal tunnel

Ulnar n. in Guyon canal Flexor tendons in carpal tunnel

Gradual numbness of fingers while driving Transverse carpal ligament (roof of carpal tunnel) Median n. in carpal tunnel

Activities or medical conditions that increase contents and pressure within tunnel may result in nerve compression.

Opponens pollicis Flexor pollicis brevis (superficial head) 1st and 2nd lumbrical mm.

Sensory distribution of median nerve

Digital nn.

Distribtion of branches of median nerve in hand Figure 65-5  Carpal Tunnel Syndrome–I.

branch, and hypertrophic scar. Ergonomic workplace alterations and avoidance of offending activities or positions are generally recommended. Neutral wrist splints, typically worn at night, initially help more than 50% of patients by maximizing the carpal tunnel diameter and minimizing nerve pressure, which is better than the natural remission rate. Local steroid injections may provide temporary pain relief with an initial success rate almost as good as surgical therapy. However, this is rarely a permanent solution, as there are frequent relapses requiring repeated injections, and there is the possible risk of flexor tendon rupture. Nonsteroidal anti-inflammatory drugs, vitamin B6, and diuretics are of no proven benefit. Surgical decompression is offered to patients with increasingly annoying sensory symptoms and progressive abnormalities on neurologic examination and electrophysiological testing (see

Fig. 65-6). Although published success rates vary significantly, the average surgical success rate is 75%; 8% of patients may worsen after surgery. Long duration of symptoms, increasing age, and the presence of workers compensation claims appear to be associated with poorer outcome. Patients with moderate electrophysiological abnormalities appear to do best, and the success rate of surgery in the absence of nerve conduction abnormalities is only 51%. Occasionally, patients present with end-stage CTS and absent motor responses on nerve conduction studies. Resolution of pain is the only realistic goal of surgical intervention for these patients. Meaningful return of thenar strength is less likely this late in the course of the neuropathy. Endoscopic techniques are being used in carpal tunnel decompression but the relative benefit of this technique compared with traditional decompressive surgery is not known.



CHAPTER 65  •  Mononeuropathies of the Upper Extremities  607

Provocative maneuvers

Tinel sign Phalen test (wrist flexion)

Digital compression test

Provocative tests elicit paresthesia in hand.

Nonsurgical management 30°—45°

Steroid injection

Median nerve Splints that maintain wrist in neutral position provide maximal carpal tunnel capacity. Surgical decompression of carpal tunnel Incision site

Compressed median nerve

Transverse carpal ligament

Median nerve

Decompressed carpal tunnel

Figure 65-6  Carpal Tunnel Syndrome–II.

PROXIMAL MEDIAN NEUROPATHIES Clinical Vignette A 36-year-old secretary complained of difficulty holding a pen and snapping her fingers to music for 6 months. The onset of weakness had been preceded by an aching pain in the volar forearm. There was no sensory loss. The patient had delivered healthy twins 3 months prior to presentation. Neurologic evaluation demonstrated weakness of the flexor pollicis longus muscle and the median-innervated portion of the flexor digitorum profundus, manifested by the inability to flex the distal phalanx of the thumb and the index and long fingers. EMG confirmed active and chronic denervation in the flexor pollicis longus, flexor digitorum profundus 2 and 3, and pronator quadratus muscles. MRI of the forearm showed evidence of atrophy in the muscles supplied by the

anterior interosseous nerve, but no other abnormalities were detected. Surgical exploration revealed entrapment of the anterior interosseous nerve by the deep head of the pronator teres muscle.

Median neuropathies arising rostral to the most proximal muscle innervated by the median nerve (the pronator teres) occur at a frequency of less than 1% of that of CTS. In a very small proportion of the population, there is a bony spur that originates from the shaft of the medial humerus, proximal to the medial epicondyle. A tendinous band called the ligament of Struthers stretches between these two structures and may represent a site of compression for the median nerve. More distally, in the antecubital fossa, the median nerve may become entrapped beneath the lacertus fibrosus, a fibrous band that runs between the tendon of the biceps and the proximal flexors of the forearm.

608  SECTION XV  •  Mononeuropathies

Pronator syndrome Hypesthesia and activity-induced paresthesias

Median n.

Compression by flexor digitorum superficialis muscle

Pain location

Flexion of middle finger against resistance Provocative maneuvers Supracondylar process

Compression by lacertus fibrosus

Compression by pronator teres muscle

Ligament of Struthers Medial epicondyle

Pronation against resistance

Lacertus fibrosus

Flexion of wrist against resistance

Anterior interosseous syndrome

Pronator teres m. Humeral head Ulnar head

Normal

Abnormal

Anterior interosseous n. Flexor digitorum superficialis m. and arch

Flexor pollicis longus m.

Hand posture in anterior interosseous syndrome due to paresis of flexor digitorum profundus and flexor pollicis longus muscles

Figure 65-7  Proximal Compression of Median Nerve.

Even more distally, the nerve can become entrapped in the substance of the pronator teres muscle or beneath the sublimis bridge of the flexor digitorum superficialis muscle (pronator teres syndrome). The clinical and electrophysiologic recognition of weakness in the distribution of the forearm muscles innervated by the median nerve is the diagnostic key (Fig. 65-7). When the median nerve lesion is most proximal, the pronator teres muscle is involved and may be atrophied. Clinical features also include pain in the volar forearm exacerbated by physical activity. There is weakness of thenar muscles and sensory loss in the thumb, index finger, long finger, and lateral aspect of the ring finger. Mechanical lesions within the axilla, secondary to shoulder dislocation or penetrating injury, may also affect the proximal median nerve, although concomitant injury of other nerves often exists. More distal lesions of the proximal median nerve include humeral fractures, elbow dislocations, tourniquet compression, and forms of penetrating trauma, such as catheterization of the antecubital veins. EMG is the crucial initial study. Imaging studies, particularly MRI of the elbow region, are indicated when EMG results are positive. Focal lesions, such as the bony origin of a ligament of Struthers or a venous infarction secondary to tourniquet compression, may be defined on neuroimaging. Conservative treatment consists of rest and antiinflammatory medications. In patients with severe symptoms

and electrodiagnostic evidence of axonal loss, surgical exploration of the median nerve in the proximal forearm should be considered.

Anterior Interosseous Neuropathies The anterior interosseous nerve is the largest motor branch of the median nerve. It does not supply any sensory innervation to the skin, but does carry sensory fibers to the muscles of the forearm and interosseous membrane. It arises about 5–6 cm below the elbow. The muscles supplied by the anterior interosseous nerve are flexor pollicis longus, flexor digitorum profundus to the second and third digits and pronator quadratus. Possible etiologies for anterior interosseous neuropathy are aberrant fibrous bands, fractures, compression by the deep head of the pronator teres muscle, pregnancy, brachial plexus neuritis, which might present as a multifocal neuropathy, or idiopathic. Anterior interosseous neuropathy usually presents with nonspecific pain in the proximal forearm. The motor symptoms include weakness of forearm pronation with the elbow flexed and weakness of distal phalanx flexion of the thumb, the index finger, and the long finger. Affected persons cannot form a circle by pinching their thumb and index finger. This presentation is similar to more proximal median neuropathies but without involvement of the pronator teres. Furthermore, there is no sensory involvement.



CHAPTER 65  •  Mononeuropathies of the Upper Extremities  609

Ulnar n. (C7, 8, T1) (no branches above elbow) Medial epicondyle Articular branch (behind condyle) Cutaneous innervation Palmar view

Flexor digitorum profundus m. (medial part only; lateral part supplied by anterior interosseous branch of median n.) Flexor carpi ulnaris m. (drawn aside) Dorsal branch of ulnar n.

Posterior (dorsal) view

Adductor pollicis m.

Palmar and dorsal interosseous mm. 3rd and 4th lumbrical mm. (turned down)

Palmar branch Superficial branch Deep branch Palmaris brevis Abductor digiti minimi Flexor digiti minimi brevis Hypothenar mm. Opponens digiti minimi Common palmar digital n. Proper palmar digital nn. (dorsal digital nn. are from dorsal branch) Dorsal branches to dorsum of middle and distal phalanges

Figure 65-8  Ulnar Nerve.

The treatment, depending on etiology, may be nonsurgical or surgical. Rest, anti-inflammatory medications, and splints can help. Surgical treatment includes exploration of the nerve.

ULNAR MONONEUROPATHIES The ulnar nerve primarily innervates intrinsic hand muscles, including all hypothenar muscles (Fig. 65-8). The muscles of the thenar eminence supplied by the ulnar nerve are the adductor pollicis and part of the flexor pollicis brevis. Only two forearm muscles have ulnar innervation, the flexor carpi ulnaris and the medial part of the flexor digitorum profundus. The ulnar nerve also supplies sensation to the medial one and a half fingers (the medial aspect of digits 4 and 5), on the dorsal surface sometimes the medial two and a half fingers (see Figs. 65-3 and 65-8). Manifestations of ulnar neuropathies vary with location and severity. Progressive motor deficits lead to the classic “claw hand,” with hyperextension of the fourth and fifth metacarpophalangeal joints and flexion of the proximal and distal interphalangeal joints (Fig. 65-9). This is most pronounced when the patient is asked to open the hand because of the unopposed action of radial nerve–innervated muscles. Similar to its median counterpart, the ulnar nerve is typically affected at two anatomic loci, the elbow and wrist, however, in reverse frequency. The majority of ulnar nerve lesions occur at the elbow (Fig. 65-10).

PROXIMAL LESIONS Clinical Vignette A 55-year-old man presented to the emergency room afraid he was having a heart attack. He had suddenly experienced sharp, shooting pain radiating from the left elbow distally, associated with tingling of the hand. Upon further questioning, the patient mentioned occasional tingling of digits 4 and 5 of the left hand for several years. He was an avid reader and frequently read with his elbows resting on his desk. The neurologic examination revealed decreased light touch in the left ring finger and little finger, splitting the ring finger. There was minimal weakness of finger abduction, and a Tinel sign at the left elbow was present. Electrodiagnostic testing showed a demyelinating left ulnar neuropathy at the elbow.

Proximal ulnar neuropathies are second only to CTS in frequency. Etiologies include external compression or entrapment at the elbow after remote elbow trauma (tardy ulnar palsy), and entrapment just distal to the elbow joint (cubital tunnel syndrome, Fig. 65-11). Numbness and paresthesias of the fifth and sometimes half of the fourth digit are the rule and may be provoked by having the patient maintain a fully flexed elbow posture for 30 to 60 seconds. Sensory signs or symptoms should not extend proximal to the wrist, in which case a C8 radiculopathy has to be considered in the differential diagnosis. Weakness of the intrinsic muscles of the hand is more common in ulnar neuropathies than in CTS. Clinically apparent involvement of ulnar forearm muscles is rarely detected. Sometimes, there is associated aching of the elbow or forearm pain. The diagnosis is confirmed by EMG. High-resolution sonography can be helpful, when precise localization of the lesion by EMG is difficult, but is not routinely performed.

DISTAL LESIONS Clinical Vignette A 40-year-old jackhammer operator noted progressive wasting of muscle bulk in the right hand. He had no pain or sensory loss. He had read about his symptoms on the Internet, and he became concerned he might have LouGehrig’s disease. On neurologic examination, the patient had difficulty holding a piece of paper between the right thumb and index finger. While attempting to do so, he flexed the distal phalanx of the thumb (Froment sign). There was atrophy of the first dorsal interosseous muscle, and fasciculations were observed within this muscle. Abduction of the little finger was of normal strength, and no sensory deficits were demonstrated. Electrodiagnostic testing was consistent with a distal left ulnar neuropathy involving only the deep motor branch. The patient regained some strength after switching jobs.

610  SECTION XV  •  Mononeuropathies

Ulnar n. Flexor carpi ulnaris m. Transverse carpal Pisiform ligament Volar carpal ligament Fibrous arcade

Management Cycling glove. Ulnar pad protects nerve from compression.

Ulnar tunnel

Deep (motor) branch of ulnar n. Superficial (sensory) branch of ulnar n.

Incision over ulnar tunnel In severe chronic cases, tunnel surgically explored and decompressed

Volar carpal ligament

Palmaris brevis m.

Transverse carpal ligament

Ulnar nerve Ulnar tunnel

Pisiform Ulnar n. Ulnar a.

Zone I (motor and sensory)

Zones of nerve compression and clinical signs Clawing of 4th and 5th fingers

Interosseous atrophy Motor findings with compression in zones I and II

Zone II (motor)

Zone III (sensory)

Sensory findings occur with compression in zones I and III Figure 65-9  Ulnar Tunnel Syndrome.

Ulnar neuropathies at the level of the wrist or palm are less common than proximal lesions. The nerve might become entrapped at the level of the ulnar tunnel or the Guyon canal. Common causes are trauma, ganglion cysts, rheumatoid arthritis, and wrist fractures. Depending on the exact site of injury, there may or may not be associated sensory symptoms (see Fig. 65-9). Sensory loss on the dorsal aspect of the medial hand points to a more proximal ulnar neuropathy with involvement of the dorsal ulnar cutaneous nerve. Ulnar neuropathies in the palm distal to the Guyon canal present with weakness confined to the ulnar muscles on the lateral aspect of the hand, particularly thumb adduction. This is secondary to weakness of the adductor pollicis, the only thenar muscle not primarily innervated by the median nerve. The first dorsal interosseous muscle is also affected, whereas abduction of the little finger may be preserved. The accompanying intrinsic muscle atrophy and the lack of sensory deficits sometimes

prompt consideration of motor neuron disease. Lesions in the palm usually result from local trauma and repetitive injury, for example, from bicycling or from occupations that use tools requiring significant intermittent pressure over the distal ulnar motor fibers (i.e., electricians, clam or oyster shuckers, and pizza cutters). EMG is essential for diagnosis. When the pressure is discontinued, significant recovery of function can occur.

DIFFERENTIAL DIAGNOSIS Motor neuron disease is a primary consideration in patients presenting with asymmetric painless atrophy of the hand intrinsics. One key differentiating feature between motor neuron disease and an ulnar nerve lesion is the frequent involvement of the abductor pollicis brevis muscle in motor neuron disease; this is innervated by the median nerve.

Medial epicondyle Long head of triceps brachii muscle Ulnar nerve Cubital tunnel Olecranon Sensory distribution

Ligament of Struthers Medial intermuscular septum

Arcuate ligament Flexor carpi ulnaris aponeurosis Common flexor aponeurosis Flexor digitorum superficialis muscle Flexor digitorum profundus muscle

Medial head of triceps brachii muscle

Cubital tunnel

Ulnar nerve Medial epicondyle

Guyon canal (ulnar tunnel)

Humeral head Ulnar head

Motor branch of intrinsic muscles of hand

Flexor carpi ulnaris muscle

Sensory branches to hand Elbow extension Fascicle of sensory and intrinsic motor fibers

Intraneural typography of ulnar n. at cubital tunnel

Dorsal cutaneous fascicle Flexor digitorum profundus fascicle

Elbow flexion Arcuate ligament

Arcuate ligament

Compression Cubital tunnel wide

Tunnel narrows, stretching nerve

Flexor carpi ulnaris fascicle

Figure 65-10  Compression of Ulnar Nerve.

Submuscular transposition of ulnar nerve

Clinical signs Motor weakness and muscle wasting in severe cases

Biceps brachii m. Brachialis m. Medial intermuscular septum

Exposure of ulnar nerve

Interosseous muscle wasting Paresthesias in distribution of ulnar nerve

Elbow flexion test

Tinel sign

90° Z-plasty incision and lengthening of flexor-pronator Flexor-pronator muscle mass Flexor carpi ulnaris m.

Triceps brachii m.

Medial epicondyle

Olecranon Anterior transposition of ulnar nerve Divided tendon of origin

Nonsurgical management

Elbow pad Furniture pad Padding of elbow or of furniture may prevent compression.

Lengthened and repaired flexor-pronator over transposed nerve

Night splinting of elbow in mild flexion prevents nocturnal paresthesias.

Figure 65-11  Cubital Tunnel Syndrome.

612  SECTION XV  •  Mononeuropathies

Lower brachial plexus injuries are accompanied by motor and sensory dysfunction in the distribution of multiple peripheral nerve territories within a single extremity. Historically, thoracic outlet syndrome, a distal T1 radiculopathy or proximal lower trunk brachial plexopathy, was considered a common cause of upper extremity neurologic symptoms. Thoracic outlet syndrome is now recognized as a rare condition that is more likely to mimic an ulnar neuropathy than CTS. Perhaps many cases of CTS were erroneously diagnosed and treated as thoracic outlet syndrome before the recognition of the frequency of CTS in the late 1950s and early 1960s. EMG defined the relative frequency of these lesions. C8 radiculopathies are less common than C7 or C6 radiculopathies but can easily be confused with an ulnar neuropathy because of their overlapping sensory territory. Medial forearm numbness and weakness of non–ulnar innervated C8 muscles (i.e., the thenar eminence, the flexor pollicis longus, and the extensor indicis proprius) provide the major diagnostic distinctions.

MANAGEMENT Conservative treatment consists of avoiding the stretch produced by a fully flexed elbow via a padded splint that prevents further direct nerve pressure. More than 50% of patients with mild nerve compression might recover with conservative therapy, although data on long-term outcome is limited. Surgical management of ulnar lesions is not as well defined as with CTS. It is even less clear who is likely to benefit from surgery, and there is no consensus on which surgical procedure is appropriate. Persistent pain, progressive motor deficits, and to a lesser extent failure to improve after 3–6 months of conservative management are reasons to consider surgery. Once sensory ulnar nerve conductions can no longer be obtained, recovery of sensory function after surgery becomes less likely. With tardy ulnar palsy, surgeons typically transpose the nerve away from the offending epicondylar groove, often with concomitant epicondylectomy (see Fig. 65-11). This procedure is associated with some risk, particularly in patients with diabetes, because the microvasculature of the nerve can be easily compromised. For cubital tunnel lesions in the absence of trauma or prior surgical procedure involving the elbow, anterior transposition seems to offer no advantage over simple decompression of the nerve.

RADIAL NEUROPATHIES Clinical Vignette An 82-year-old man was seen in urgent consultation for a possible stroke. He had awoken in his chair during the late morning with weakness of the right arm. The night prior, he had taken a sleeping pill for the first time in his life. The neurologic examination revealed weakness of elbow flexion in the semi-pronated position (brachioradialis muscle), wrist extension, and finger extension. The brachioradialis reflex was absent, whereas the triceps reflex and triceps strength were preserved. There was sensory loss to

Posterior view Radial n. (C5, 6, 7, 8, T1) Superficial (terminal) branch Deep (terminal) branch Lateral epicondyle Anconeus m. Brachioradialis m. Extensor carpi radialis longus m. Supinator m. Extensor carpi radialis brevis m. Extensor carpi ulnaris m.

Extensor-supinator group of muscles

Extensor digitorum m. and extensor digiti minimi m. Extensor indicis m. Extensor pollicis longus m. Abductor pollicis longus m. Extensor pollicis brevis m. Posterior interosseous n. (continuation of deep branch of radial n. distal to supinator m.) Superficial branch of radial n.

From axillary n.

Superior lateral cutaneous n. of arm

From radial n.

Inferior lateral cutaneous n. of arm Posterior cutaneous n. of arm Posterior cutaneous n. of forearm Superficial branch of radial n. and dorsal digital branches

Dorsal digital nn.

Cutaneous innervation from radial and axillary nn.

Figure 65-12  Radial Nerve in Forearm.

light touch and pinprick on the dorsal aspect of the forearm and dorsolateral hand. Electrodiagnostic testing performed on the day of presentation was suggestive of an acute right radial neuropathy at the spiral groove. At the time of his follow-up visit 4 weeks later, the patient had completely recovered.

The radial nerve is formed by fibers from all three trunks of the brachial plexus, hence from roots C5 to T1. It primarily supplies the extensor muscles of the arm, forearm, and fingers and one flexor of the arm, the brachioradialis (see Fig. 65-1). It also provides the sensory innervation to the dorsal arm, the dorsolateral aspect of the hand, and the dorsum of the first three and a half, sometimes two and a half fingers (Fig. 65-12).

PREDOMINANT MOTOR RADIAL NEUROPATHIES Radial neuropathies most commonly occur at the midhumeral level near the spiral groove, secondary to external compression



CHAPTER 65  •  Mononeuropathies of the Upper Extremities  613

Motor signs

Paresthesia and Posterior interosseous hypesthesias syndrome Pain and tenderness Pain radiation

Proximal compression. Loss of wrist and finger extension

Sensory signs in radial tunnel syndrome Provocative tests for radial tunnel syndrome

Radial nerve

Supination against resistance Resistive extension of middle finger

Recurrent radial artery Superficial radial nerve Posterior interosseous nerve

Provocative tests elicit pain over radial tunnel.

Vascular leash of Henry Extensor carpi radialis brevis muscle Fibrous arcade of Frohse Supinator muscle Posterior interosseous nerve Innervation of extensor muscles Tendon of brachioradialis muscle Superficial radial nerve at wrist

Compression of nerve in axilla or upper arm in patient sleeping with arm over chair back, edge of bed, etc, or by crutch

Figure 65-13  Radial Nerve Compression.

(Fig. 65-13). This can occur as a result of impaired consciousness during anesthesia or due to drug or alcohol intoxication (“Saturday night palsy”). These lesions primarily present with wrist and finger drop but little or no pain. Sensory signs and symptoms are often elusive. Elbow extension is spared because the branches of the triceps originate proximal to the spiral groove. The brachioradialis reflex is typically diminished or lost, whereas the triceps and biceps reflexes are unaffected. A potentially confounding examination feature is apparent weakness of ulnar innervated finger abduction that appears concomitant with wrist drop. The full strength of these ulnar muscles requires at least partial wrist extension. Testing the strength of finger abduction while placing the hand and forearm flat on a hard and flat surface circumvents this problem and prevents false localization. The posterior interosseous nerve is analogous to the anterior interosseous nerve because it is a distal, predominantly motor

branch of a major peripheral nerve trunk. Posterior interosseous neuropathies commonly occur with fractures of the proximal radius and sometimes have a delayed onset. The posterior interosseous nerve can also be compromised by soft tissue masses. A syndrome of pain and weakness in the muscles innervated by the posterior interosseous nerve may occur in patients who perform repetitious and strenuous pronation/supination movements, which in some instances leads to intermittent posterior interosseous nerve compression by the fibrous edge of the arcade of Frohse (the proximal aspect of the supinator muscle). Entrapment may also develop secondary to a hypertrophied or anomalous supinator muscle. The extensor carpi radialis longus and brevis and the brachioradialis muscles are innervated by branches exiting the radial nerve before the origin of the posterior interosseous nerve; therefore, finger drop, rather than wrist drop as with a more proximal radial nerve lesion, is the dominant manifestation. The extensor carpi ulnaris, however, is

614  SECTION XV  •  Mononeuropathies

weak, which leads to radial deviation of the hand during wrist extension. There is no sensory loss. Pain near the lateral epicondyle of the humerus, extending distally, may occur, as the posterior interosseous nerve gives off sensory fibers supplying the interosseous membrane and joints of the forearm.

PREDOMINANT SENSORY RADIAL NEUROPATHIES The superficial radial nerve, a primary distal sensory branch, may be injured in isolation with external pressure at the wrist, for example, with handcuff injuries. These lesions are readily recognized by the distribution of sensory symptoms on the dorsolateral portion of the hand. Weakness does not occur.

MANAGEMENT Radial neuropathies usually result from monophasic external compression. They are almost always treated conservatively and successfully.

MONONEUROPATHIES OF THE MEDIAL AND POSTERIOR CUTANEOUS NERVES OF THE FOREARM Isolated injuries of the medial cutaneous nerve of the forearm are rare (see Fig. 65-3). Sensory symptoms in the medial volar forearm are more commonly a result of more proximal injuries to the lower trunk or medial cord of the brachial plexus or to the C8 nerve root. Nerve injuries at these levels are associated with additional clinical findings, particularly hand weakness. Sensory symptoms on the posterior forearm from isolated injuries to the posterior cutaneous nerve of the forearm are equally rare.

DIAGNOSTIC APPROACH TO MONONEUROPATHIES EMG and Nerve Conduction Studies Myelin loss manifests electrodiagnostically in three ways: focal slowing, differential slowing (also known as temporal dispersion), and conduction block. Focal slowing occurs when all nerve fibers are affected, approximately to the same extent, in one precise anatomic area. Impulse transmission is slowed uniformly in all fibers at that location. When patients have evidence of differential slowing, that is, temporal dispersion, demyelination is typically multifocal, varying in severity in different fibers within the same nerve. Temporal dispersion is the EMG hallmark of acquired demyelinating polyneuropathies, such as Guillain–Barré syndrome, and is not typically seen in focal mononeuropathies. Primary conduction block is consistent with a demyelinating process in one or more locations that is sufficient to prohibit impulse transmission across involved sections of affected nerve fibers, and this causes clinical weakness. Because axonal integrity is not compromised, muscle wasting does not occur. Since unmyelinated fibers are also not affected,

pain and thermal sensation are relatively spared. Conduction block commonly occurs with ulnar neuropathies at the elbow, radial neuropathies at the spiral groove, and peroneal neuropathies at the fibular head. With motor axonal disruption, the axon is separated from the anterior horn cell and degenerates. Myofibers are deprived of the trophic influence provided by that axon, with resultant atrophy greater than that produced by disuse. Abnormal spontaneous activity characterized by fibrillation potentials and positive sharp waves appears on needle examination, and the number of activated motor unit potentials decreases. Similarly, the loss of unmyelinated axons mediating nociceptive, thermal, and autonomic functions usually produces clinical features different from primary demyelinating insults. These are characterized by loss of pain and thermal perception, hypersensitivity to touch, changes in sweat production, and sometimes vasomotor changes secondary to focal dysautonomia. Clinical features of axon loss can be superimposed upon those associated with the demyelinating component of the nerve injury. The various mononeuropathies do not have identical pathophysiologic signatures. Some, such as CTS, are initially characterized by focal slowing (Fig. 65-14), whereas others may preferentially produce a demyelinating conduction block, such as an ulnar neuropathy at the elbow, or axon loss as with a primary laceration, or a combination of the above. EMG and nerve conduction studies provide the means to confirm the existence, location, pathophysiology, and severity of most mononeuropathies. However, electrodiagnosis has important limitations. Ideally, the injured nerve needs to be accessible to stimulation at multiple levels, including at least one site proximal to the site of a demyelinating lesion. This can be technically difficult, even impossible, with proximal nerve segments that are deep and in close proximity to other nerve elements. Localization can also be predicted by the pattern of muscles demonstrating changes of denervation on needle examination. However, the major limitation of this methodology is anatomic as nerve branching is erratic. For example, the ulnar nerve has no branches in the upper arm, two near the elbow, and then none until the hand. The other limitation is selective fascicular involvement, whereby a nerve injury at a given location may not result in denervation of all muscles innervated distal to that injury. Understandably, a false estimate of nerve injury location may result. False-positive results can result from cold limb temperature, failure to recognize normal anatomic variants, or poor technique. Caution is required not to overcall on the basis of borderline data. Ideally, the presence of abnormalities in two concordant parameters enables conclusive diagnosis. Falsenegative results also occur. Approximately 10% of patients with clinical histories strongly suggestive of CTS might have normal electrodiagnostic evaluations.

Other Testing Modalities Although most mononeuropathies occur secondary to recognizable compression, stretch, or entrapment mechanisms, some seem to be idiopathic. Additional testing, particularly MRI, may be diagnostic when mononeuropathies develop in atypical locations or under unusual circumstances.



CHAPTER 65  •  Mononeuropathies of the Upper Extremities  615

Electromyography (EMG) EMG detects and records electric activity or potentials within muscle in various phases of voluntary contraction Nerve impulse (action potential)

Bipolar recording needle

First dorsal interosseous muscle

EMG of dorsal interosseous muscle (ulnar innervation)

Normal Action potential Needle insertion

Maximal contraction

Abnormal fibrillation

Denervation positive waves

Fasciculation

Compression–induced denervation produces abnormal spontaneous potentials

Stimulation at wrist Motor (recording electrodes)

Voltage

Stimulating electrode

Decreased amplitude

Increased threshold Normal threshold Normal latency Increased latency

Conduction Distance between electrodes = velocity Difference in elbow and wrist latency

Voltage

Distance

Stimulation at elbow

Normal amplitude

Time

Nerve conduction studies

Sensory (recording electrodes)

Increased threshold for depolarization, increased latency, and decreased conduction velocity suggest compression neuropathy Nerve conduction studies evaluate ability of nerve to conduct electrically evoked action potentials. Sensory and motor conduction stimulated and recorded.

Figure 65-14  Electrodiagnostic Studies in Compression Neuropathy.

PROGNOSIS OF MONONEUROPATHIES Prognosis primarily depends on whether the injury has a demyelinating or axonal pathophysiologic mechanism or both. If axonal, recovery depends on the number of axons damaged, the persistence or resolution of the causative insult, the distance between the site of injury and the innervated muscle or cutaneous region, and the patient’s age and comorbidities. Demyelinating lesions usually resolve spontaneously after removal of focal compression or entrapment. ADDITIONAL RESOURCES American Association of Neuromuscular and Electrodiagnostic Medicine. Available at: http://www.aanem.org. Accessed June 13, 2011. The information on this website includes a list of suggested reading for physicians as well as educational material for patients with various neuromuscular disorders.

Bland JDP. Do nerve conduction studies predict the outcome of carpal tunnel syndrome? Muscle Nerve 2001;24:935-940. This study examines factors influencing the outcome of surgical carpal tunnel decompression. Bland JDP. Treatment of carpal tunnel syndrome. Muscle Nerve 2007;36:167-171. This review article summarizes the current knowledge about different treatment modalities for carpal tunnel syndrome. Dumitru D, Amato A, Zwarts M. Electrodiagnostic Medicine. 2nd ed. Philadelphia, PA: Hanley&Belfus; 2002. This textbook is an excellent reference for physicians interested in disorders of the peripheral nervous system and electrophysiological techniques. Marshall S, Tardif G, Ashworth N. Local corticosteroid injection for carpal tunnel syndrome. Cochrane Database of Systematic Reviews 2007;Issue 2. Art. No.: CD001554. DOI: 10.1002/14651858.CD001554.pub2. This article reviews data from 12 randomized or quasi-randomized studies regarding the effectiveness of local corticosteroid injection for carpal tunnel syndrome. O’Connor D, Marshall S, Massy-Westropp N. Non-surgical treatment (other than steroid injection) for carpal tunnel syndrome. Cochrane Database of Systematic Reviews 2003; Issue 1. Art. No.: CD003219. DOI: 10.1002/14651858.CD003219. This review article evaluates the effectiveness of conservative treatment options (other than corticosteroid injection) for

616  SECTION XV  •  Mononeuropathies

carpal tunnel syndrome based on data from 21 randomized or quasi-randomized studies. Padua L, Padua R, Aprile I, et al. Multiperspective follow-up of untreated carpal tunnel syndrome. A multicenter study. Neurology 2001;56:14591466. The authors evaluate the natural history of untreated carpal tunnel syndrome over a 10-15 month follow-up period. Scholten RJPM, Mink van der Molen A, Uitdehaag BMJ, et al. Surgical treatment options for carpal tunnel syndrome. Cochrane Database of Systematic Reviews 2007;Issue 4. Art. No.: CD003905. DOI: 10.1002/14651858.CD003905.pub3. The authors compare the outcome of various surgical techniques for carpal tunnel syndrome, including data from 33 randomized controlled trials. Sunderland S. Nerves and Nerve Injuries. 2nd ed. Edinburgh, Scotland: Churchill Livingstone; 1978. This outstanding textbook provides a detailed

description of the anatomy and physiology of peripheral nerves and outlines the various mechanisms of nerve injury in great depth. Verdugo RJ, Salinal RS, Castillo J, et al. Surgical versus non-surgical treatment for carpal tunnel syndrome. Cochrane Database of Systematic Reviews 2003;Issue 3. Art. No.: CD001552. DOI: 10.1002/14651858. CD001552. The authors summarize two randomized controlled trials comparing surgical treatment of carpal tunnel syndrome with splinting and pool data from both trials for secondary outcomes. Zlowodzki M, Chan S, Bhandari M, et al. Anterior transposition compared with simple decompression for treatment of cubital tunnel syndrome. J Bone Joint Surg A 2007;89:2591-2598. This meta-analysis of four randomized controlled trials compares the efficacy of simple decompression with anterior transposition of the ulnar nerve in compression neuropathies at the elbow.

Mononeuropathies of the Lower Extremities

66 

Gisela Held and Miruna Segarceanu

SCIATIC NEUROPATHIES Clinical Vignette An 82-year-old frail woman fell in her home. She sustained a hip fracture, which necessitated surgical repair. Post­ operatively, she received anticoagulation. Two days later, she had discomfort in her right buttock and hip and foot weakness. Within 24 hours, marked buttock pain and paralysis of all muscles below the right knee and numbness developed. Computed tomographic (CT) scan revealed pelvic hematoma. Despite surgical drainage of 2 L of blood, there was little improvement in sciatic nerve function. Electromyography (EMG) confirmed a primary sciatic neuropathy.

T

he sciatic nerve is the body’s largest nerve, receiving con­ tributions primarily from the L5, S1, and S2 nerve roots, but also carrying L4 and S3 fibers (Fig. 66-1). It has two primary divisions: the laterally situated more superficial peroneal nerve and the more medially placed tibial nerve (see Fig. 66-1). These separate into two distinct nerves in the mid- to distal thigh. The sciatic nerve and its branches innervate the hamstrings (biceps femoris, semimembranosus, and semitendinosus muscles), distal adductor magnus, anterior and posterior lower leg com­ partments, and intrinsic foot musculature. Through sensory branches of the tibial nerve (sural, medial and lateral plantar, and calcaneal) and the superficial peroneal nerve, the sciatic nerve also supplies sensation to the skin of the entire foot and the lateral and posterior lower leg.

ETIOLOGY Sciatic neuropathies can be due to hip arthroplasty, pelvic or femoral fractures, or posterior dislocation of the hip. Like femoral neuropathies, they are sometimes caused by a pro­ longed lithotomy position, presumably from stretching of the nerve in individuals who are anatomically predisposed. Occa­ sionally, sciatic neuropathies develop from external pressure in patients who are comatose or immobilized for protracted periods such as with drug overdose. They may result from traumatic mechanisms including misplaced injections into the inferior medial quadrant of the buttock. Mass lesions including nerve sheath tumors and external compression from hematoma, aneu­ rysm, endometriosis, and other mechanisms have been described. Sciatic neuropathies may occur in patients with systemic vasculitis.

CLINICAL PRESENTATION Acute sciatic neuropathies typically present with distal leg weak­ ness, pain, and sensory loss. Foot pain is a frequent complaint. Because of predominant affliction of the peroneal division, the weakness often manifests itself as foot drop and needs to be differentiated from a common peroneal neuropathy at the fibular head. Weakness of the more proximal muscles (ham­ strings) and of foot plantar flexion and inversion (gastrocnemius, tibialis posterior) helps differentiate between the two entities. The ankle jerk and internal hamstring reflex are usually depressed or absent. Sensory loss and dysesthesia of the sole and dorsum of the foot and posterolateral lower leg are common.

DIFFERENTIAL DIAGNOSIS A lumbosacral plexus lesion is the primary consideration in most patients with sciatic neuropathies, when findings clearly encom­ pass a territory outside the peroneal nerve. Diminished sensa­ tion on the posterior thigh points to a concomitant neuropathy of the posterior femoral cutaneous nerve, which exits the greater sciatic foramen in proximity to the sciatic nerve. Injury to the perineal branches of this nerve leads to sensory loss on the scrotum or labia majora. Hip extension and abduction should be preserved in sciatic neuropathies. When clinical or EMG evidence suggests gluteal muscle involvement, primary lesions within the pelvis, such as benign tumors, for example, schwannoma, or malignant processes, particularly, lymphoma are considerations. Piriformis syndrome is a poorly understood disorder that is phenomenologically similar to the thoracic outlet and tarsal tunnel syndromes. The piriformis muscle lies deep to the gluteal muscles; it originates from the sacral spine and attaches to the greater trochanter of the femur. The sciatic nerve passes post­ erior to the piriformis muscle. It is postulated that acute or chronic injury of the muscle may cause irritation of the sciatic nerve, resulting in posterior thigh and gluteal pain. Patients with an aberrant course of the nerve through the muscle are particu­ larly predisposed to this condition. Objective clinical or electro­ diagnostic evidence of sciatic neuropathy is not seen in most patients in whom piriformis syndrome is suspected.

PERONEAL NEUROPATHIES Clinical Vignette A 44-year-old woman presented with right foot drop and numbness of the dorsum of the right foot. She had first

618  SECTION XV  •  Mononeuropathies

Sciatic Nerve (L4, L5; S1, S2, S3) Posterior femoral cutaneous nerve

Cutaneous innervation

Inferior cluneal nerve Perineal branches

Greater sciatic foramen Sciatic nerve Common peroneal segment of sciatic nerve

Tibial segment of sciatic nerve Long head (divided) of biceps femoris muscle

Short head of biceps femoris muscle

Adductor magnus muscle (also supplied by obturator nerve)

Long head (divided) of biceps femoris muscle

Semitendinosus muscle Semimembranosus muscle

Posterior femoral cutaneous nerve

Common peroneal nerve

Tibial nerve Articular branch Plantaris muscle Medial sural cutaneous nerve

Articular branch Lateral sural cutaneous nerve

Common peroneal nerve (via lateral sural cutaneous nerve)

Peroneal communicating branch

Gastrocnemius muscle Sural nerve Soleus muscle Tibial nerve Medial calcaneal branches

From sciatic nerve

Superficial peroneal nerve Sural nerve

Lateral calcaneal branches Lateral dorsal cutaneous nerve

Medial and lateral plantar nerves

Tibial nerve (via medial calcaneal branches)

Tibial Nerve (L4, L5; S1, S2, S3) Tibial nerve Medial sural cutaneous nerve (cut) Articular branches Plantaris muscle Gastrocnemius muscle Nerve to popliteus muscle Popliteus muscle Crural interosseous nerve Soleus muscle Flexor digitorum longus muscle Tibialis posterior muscle Flexor hallucis longus muscle Sural nerve (cut) Lateral calcaneal branch Medial calcaneal branch Flexor retinaculum (cut)

Common peroneal nerve Articular branch Lateral sural cutaneous nerve (cut) Flexor retinaculum (cut) Tibial nerve Medial plantar nerve to: Flexor digitorum brevis muscle Abductor hallucis muscle, Flexor hallucis brevis muscle 1st lumbrical muscle, Articular branch, Cutaneous branches, Proper plantar digital nerves

Medial and lateral calcaneal branches From tibial nerve

Cutaneous innervation of sole Medial calcaneal branches (S1, 2) Sural nerve Medial plantar (S1, 2) nerve (L4, 5) Lateral plantar nerve (S1, 2)

Lateral plantar nerve to: Quadratus plantae muscle, Abductor digiti minimi muscle Deep branch to: 1st, 2nd, 3rd plantar interossei muscles; 2nd, 3rd, 4th lumbrical muscles; Adductor hallucis muscle, articular branches

Saphenous nerve (L3, 4)

Superficial branch to: Flexor digiti minimi brevis muscle, 4th interossei muscles, Proper plantar digital nerves, cutaneous branches

Figure 66-1  Sciatic, Peroneal, and Tibial Nerves.

noted difficulty walking 7 weeks earlier when she tripped over a curb and fell. She had intentionally lost 70 pounds over the last year. To accomplish this, she had done frequent exercises in a squatting position on the floor. There was no history of recent trauma to the back or buttock, or of radicular leg pain. On examination of the patient, there was tenderness to palpation at the proximal lateral knee, but there was no discrete mass. On motor examination, she had weakness in right toe extension, foot dorsiflexion, and foot eversion. Plantar flexion and inversion of the foot, knee flexion, and

hip abduction were preserved. Sensory examination was notable for reduced pinprick and light touch on the dorsum and first web space of the right foot. Muscle stretch reflexes were normal. Nerve conduction studies revealed conduction block on peroneal motor studies across the fibular head; needle electromyography showed a reduced recruitment in peroneal muscles with sparing of the short head of the biceps femoris; this is consistent with a demyelinating peroneal neuropathy. Her weakness improved significantly over the following weeks, and 3 months later, she had recovered completely.



CHAPTER 66  •  Mononeuropathies of the Lower Extremities  619

Common fibular (peroneal) nerve (phantom)

Lateral sural cutaneous nerve (phantom)

Cutaneous innervation

Articular branches Biceps femoris tendon Common fibular (peroneal) nerve (L4, 5, S1, 2) Head of fibula Fibularis (peroneous) longus muscle (cut) Superficial fibular (peroneal) nerve Branches of lateral sural cutaneous nerve Fibularis (peroneus) longus muscle Fibularis (peroneus) brevis muscle

Medial dorsal cutaneous nerve Intermediate dorsal cutaneous nerve Inferior extensor retinaculum (partially cut)

Recurrent articular nerve Extensor digitorum longus muscle (cut) Deep fibular (peroneal) nerve Tibialis anterior muscle

Extensor digitorum longus muscle

Lateral sural cutaneous nerve Superficial fibular (peroneal) nerve

Deep fibular (peroneal) nerve

Extensor hallucis longus muscle

Lateral branch of deep fibular (peroneal) nerve to Extensor hallucis brevis and Extensor digitorum brevis muscle Medial branch of deep fibular (peroneal) nerve

Sural nerve via lateral dorsal cutaneous branch Compression of common peroneal nerve over fibular head by cast, in debilitated patient sitting with legs crossed, or in inebriate sleeping on side on hard surface

Lateral dorsal cutaneous nerve (branch of sural nerve) Dorsal digital nerves

Figure 66-2  Peroneal Nerve.

Axons originating from the L4, L5, S1 and S2 roots, primar­ ily L5 nerve root fibers, come together to form the common peroneal nerve. It is one of the two major divisions of the sciatic nerve and separates from it as a distinct nerve in the midto distal thigh. It travels through the popliteal fossa and gives off the lateral sural cutaneous nerve, which unites with the medial sural cutaneous nerve (a branch of the tibial nerve) to form the sural nerve. The lateral cutaneous nerve of the calf also branches off in the popliteal fossa. It provides sensation to the skin of the lateral leg just below the knee. On its course around the fibular head, the common peroneal nerve is very superficial and covered only by skin and subcutaneous tissue. It then pierces through a fibrous, sometimes tight opening in the peroneus longus muscle (fibular tunnel) and divides into superficial and deep branches.

ETIOLOGY Common peroneal neuropathy is the most frequent lower extremity mononeuropathy. The common peroneal nerve is most susceptible to external compression at the fibular head, where it is very superficial (Fig. 66-2). Predisposing causes include recent substantial weight loss, habitual leg crossing, or prolonged squatting. External devices such as casts, braces, and tight bandages can also cause peroneal neuropathy. Diabetes mellitus, vasculitis, and rarely hereditary tendency to pressure palsy (HNPP) are other etiologic conditions. An acute anterior or lateral compartment syndrome below the knee can also lead to acute common, deep, or superficial peroneal neuropathies. Patients with insidious onset and progressive course require evaluation for mass lesions, including a Baker cyst or ganglion, osteoma, or schwannoma (Fig. 66-3). The common peroneal

620  SECTION XV  •  Mononeuropathies

A. Coronal T1-weighted MRI demonstrates an oval mass B. Axial T1-weighted post gadolinium-enhanced fat-saturated MRI of left peroneal nerve (arrows)

demonstrating enhancing peroneal nerve schwannoma with central myxoid degeneration (arrow) near fibula (arrowhead).

Figure 66-3  Peroneal Nerve Schwannoma.

nerve is sometimes injured iatrogenically. Knee positioning and padding to decrease pressure on the peroneal nerve in the oper­ ating room and intensive care unit are important to prevent an acute compression neuropathy. Rarely, laceration of the pero­ neal nerve occurs with arthroscopic knee repair or direct pen­ etrating trauma. Isolated superficial peroneal neuropathies are uncommon but can result from lateral compartment syndrome, local trauma, or rarely an isolated schwannoma.

CLINICAL PRESENTATION Most peroneal neuropathies involve the common peroneal nerve at the fibular head causing weakness of foot dorsiflexion and eversion (see Fig. 66-1). Ambulation reveals a “steppage gait” with compensatory hip and knee flexion in order to lift the foot off the floor. The foot might hit the floor with a slap, as the patient has poor control over its movements. With the less frequently occurring deep peroneal neuropathies, there is weakness of the tibialis anterior, extensor hallucis, extensor digi­ torum longus, and extensor digitorum brevis. Primary superfi­ cial peroneal neuropathies cause weakness of the peroneus longus and brevis muscles, which are mainly responsible for foot eversion. Sensory symptoms are limited to the web space between the first and second toes with deep peroneal neuropathies. Superfi­ cial peroneal neuropathies can diminish sensation on the dorsum of the foot and lateral distal half of the leg. Common peroneal sensory symptoms occur on the dorsal foot surface extending up the lateral half of the leg. EMG involvement of the short head of the biceps femoris is the major distinguishing feature with proximal peroneal division sciatic neuropathies. Biceps femoris function cannot be isolated clinically; therefore, EMG is crucial to diagnosis.

DIFFERENTIAL DIAGNOSIS Differential diagnoses of peroneal neuropathies include anterior horn cell disease, L5 radiculopathy, lumbosacral trunk or plexus lesions, sciatic neuropathy, or rarely neuromuscular junction disorders. Sciatic neuropathies are sometimes mistakenly diag­ nosed as peroneal neuropathies. The peroneal division of the sciatic nerve is more superficial than its tibial division and there­ fore external compressive proximal lesions of the sciatic nerve involve the common peroneal nerve more than the tibial nerve. Most sciatic neuropathies also affect some tibial nerve functions with weakness of knee flexion, foot plantar flexion, and foot inversion. The ankle jerk is characteristically depressed or absent if there is involvement of the tibial component of the sciatic nerve, whereas it is typically unaffected in primary pero­ neal neuropathies. Sensory loss involves the common peroneal territory described above and the plantar and lateral foot surface. L5 radiculopathy remains a consideration in any patient with a foot drop. Back pain is common with nerve root lesions and is uncommon in peroneal neuropathies; the pain is typically radic­ ular, with buttock, thigh, and leg components sometimes aggra­ vated by positional change. The distribution of weakness is very important; involvement of muscles outside the peroneal nerve territory, such as the tibialis posterior or gluteus medius inner­ vated by the L5 root is critical. Isolated weakness of great toe extension occurs with mild L5 radiculopathy but is uncommon in peroneal neuropathy. In moderate–severe L5 radiculopathies, foot inversion will be weak because of involvement of the tibial nerve innervated posterior tibial muscle. Uncommonly, hip abduction weakness due to involvement of gluteus medius, an L5 muscle supplied by the superior gluteal nerve, is notice­ able. Careful evaluation of patients with an L5 root lesion should demonstrate these deficits in addition to weakness of the peroneal innervated muscles. The distribution of sensory symp­ toms in L5 radiculopathies overlaps significantly with peroneal neuropathies, although L5 nerve root sensory loss may extend



CHAPTER 66  •  Mononeuropathies of the Lower Extremities  621

more proximally onto the lateral leg. Lumbosacral plexus lesions rarely enter the differential diagnosis of peroneal neuropathies but are a consideration in patients who have a foot drop, proximal lower extremity pain, and motor and sensory findings extending beyond a single peripheral nerve or root distribution. Involvement of hip abduction and extension, clinically and/or by EMG, suggests plexus localization. Polyneuropathy is easily distinguished from peroneal neuropathy, the clinical examina­ tion and EMG usually reveal bilateral widespread motor and sensory abnormalities, not confined to a particular nerve or root distribution, muscle tendon reflexes are depressed or absent. The possibility of motor neuron disease exists with insidious onset of a foot drop without pain or sensory findings. Motor neuron disease or amyotrophic lateral sclerosis is a slowly pro­ gressive disorder and may be associated with evidence of upper motor neuron dysfunction. In patients with myasthenia, a dis­ order of neuromuscular transmission, unilateral foot drop is not seen. Distal myopathies may produce foot drop but usually do so bilaterally, and there is often evidence of weakness elsewhere. Unilateral foot drop with or without sensory symptoms can occur with disorders of the spinal cord or parasagittal frontal lobe; these conditions are usually associated with hyperreflexia; magnetic resonance imaging (MRI) is useful to diagnose these conditions.

A

TIBIAL NEUROPATHIES Clinical Vignette A 39-year-old man presented to the emergency room for severe pain and swelling of the right leg associated with difficulty walking. On neurologic examination, there was weakness of right foot plantar flexion and inversion, and flexion of the toes. The ankle jerk was absent. Doppler ultrasound and an MRI of the right knee revealed a ruptured Baker’s cyst in the popliteal fossa. Surgical removal of the synovial cyst resulted in resolution of the pain and foot weakness.

Tibial nerve fibers arise primarily from L5, S1 and S2 nerve roots with some contributions from L4 and S3. The tibial nerve leaves the sciatic nerve in the mid- to distal thigh (see Fig. 66-1). The medial sural cutaneous nerve comes off in the popliteal fossa and joins the lateral sural cutaneous nerve (a branch of the common peroneal nerve) in the distal calf to form the sural nerve, which supplies the skin of the lateral aspect of the foot and the posterior lower leg to a variable degree. After innervat­ ing the gastrocnemius and soleus muscles, the nerve travels distally between the tibialis posterior and gastrocnemius muscles. It sends branches to the tibialis posterior, flexor digitorum longus, and flexor hallucis longus before entering the tarsal tunnel under the flexor retinaculum. Here, the tibial nerve typi­ cally divides into the medial plantar, lateral plantar, and medial calcaneal nerves. Although the medial calcaneal nerve is a purely sensory branch to the medial heel, the medial and lateral plantar nerves are mixed nerves innervating the intrinsic foot muscles as well as the skin of the sole.

B Coronal (A) and axial (B) proton density fat-saturated MR images demonstrate discrete T2 bright tumor that enlarges the nerve sheath (arrow). Figure 66-4  Posterior Tibial Neurofibroma.

PROXIMAL LESIONS Proximal tibial neuropathies may result from Baker’s cysts, ganglia, tumors (Fig. 66-4), or rarely indirectly from severe ankle strains, the latter presumably resulting from traction injury. They rarely occur in isolation. They are characterized by weakness of foot plantar flexion and inversion; although flexion, abduction, and adduction of the toes may be affected, these latter functions are difficult to evaluate clinically. The ankle jerk is absent if the neuropathy occurs proximal to the branch points of the gastrocnemius-soleus complex. Sensory loss occurs on the heel and plantar foot surface.

TARSAL TUNNEL SYNDROME Tarsal tunnel syndrome (TTS), a distal tibial neuropathy, presents primarily with sensory symptoms. It is classified as an entrapment neuropathy of the posterior tibial nerve and of its primary branches, the medial and lateral plantar nerves, at the ankle (See Fig. 66-3). Although well described, there is contro­ versy regarding its prevalence as electrophysiological documen­ tation is infrequent. Whether this reflects its uncommon

622  SECTION XV  •  Mononeuropathies

occurrence or the inadequate sensitivity of diagnostic proce­ dures is unclear. Fractures, ankle sprain, foot deformities due to rheumatoid arthritis or other conditions, varicose veins, tenosy­ novitis and fluid retention have been implicated as possible etiologies. Patients typically present with burning pain and numbness on the sole of one or both feet. Symptoms may occur while weight bearing and are often exacerbated at night. In wellestablished instances, examination may disclose intrinsic plantar surface muscle atrophy. However, weakness of these muscles is difficult to appreciate because the more proximal long toe flexors in the leg mask weakness from the involved short toe flexors within the foot. Toe abduction weakness occurs early but is difficult to assess even in healthy individuals. Sensory loss is confined to the sole of the foot; there is sparing of the lateral foot (sural distribution), the dorsum of the foot (peroneal terri­ tory), and the instep (saphenous nerve). Muscle stretch reflexes are unaffected. A Tinel sign elicited from the tibial nerve at the ankle is supportive, although not confirmatory. If TTS results from nerve entrapment, simulating carpal tunnel syndrome, EMG should demonstrate demyelination via prolongation of the distal latencies. However, prolonged tibial motor and mixed nerve distal latencies from the medial and lateral plantar nerves are rarely seen in patients with suspected TTS. Absent mixed nerve responses from the plantar nerves may be seen, but have limited localizing value because they also occur in some seemingly healthy elderly individuals and in those with an underlying polyneuropathy. Fibrillation potentials in tibial innervated foot muscles must be interpreted with similar caution. Imaging in suspected TTS includes radiographs to detect osseous abnormalities involving the tarsal tunnel region and CT, if severe ankle osteoarthritic changes and exostosis are considered. Initial treatment of TTS is nonoperative, consisting of foot­ wear modification, particularly avoidance of high-heeled and poorly fitting footwear. Anti-inflammatory medications may help. Steroid injections, augmented with lidocaine, can be helpful if flexor tenosynovitis is suspected. Care is taken to avoid an intraneural injection with the unlikely possibility of causing local nerve sclerosis. Hind foot valgus deformities may benefit from orthoses. When nonoperative measures fail in TTS, surgi­ cal intervention may be considered. The results of surgical decompression are not always rewarding. Release of the flexor retinaculum and fibrous origin of the abductor hallucis muscle is required. Local flexor tenosynovitis is resected with radical tenosynovectomy. Enlarged and varicose veins are ligated and resected. Postoperatively, an open shoe is used with partial weight bearing for 2 weeks.

FEMORAL NEUROPATHIES Clinical Vignette A 63-year-old man with hemophilia presented with right knee buckling a week after a motor vehicle accident. He also complained of dull pain in the right flank radiating into the thigh and knee. He could not raise his right leg off the bed. There was no back pain or sphincter dysfunction. The neurologic examination revealed weakness of the right iliopsoas

and quadriceps muscles, an absent right quadriceps muscle stretch reflex, and diminished sensation to touch and pinprick over the anterior thigh and medial leg below the knee. Pelvic CT demonstrated a hemorrhage of the right iliacus and psoas muscles in the pelvis. Surgery revealed a large hematoma compressing the femoral nerve. This was successfully drained. Postoperatively, the patient gradually improved, regaining significant function within a week.

The femoral nerve comes off the lumbar plexus and is formed by the posterior divisions of the L2–L4 roots (Fig. 66-5). It travels between two important hip flexors, the iliopsoas and iliacus muscles, which it innervates. Approximately 4 cm proxi­ mal to the inguinal ligament, the femoral nerve is covered by a tight fascia at the iliopsoas groove. It exits the pelvis by passing beneath the medial inguinal ligament to enter the femoral tri­ angle just lateral to the femoral artery and vein. Here, the nerve separates into the anterior and posterior divisions. The anterior division innervates the sartorius muscle and the anteromedial skin of the thigh via the medial cutaneous nerve of the thigh. The posterior division gives off muscular branches to the pec­ tineus and quadriceps femoris muscles as well as the saphenous nerve, a cutaneous branch to the skin of the inner calf. The nerve can be compressed anywhere along its course, but it is particularly susceptible within the body of the psoas muscle, at the iliopsoas groove, and at the inguinal ligament.

ETIOLOGY Femoral mononeuropathies are infrequent. Historically, dia­ betic femoral neuropathies were considered common, although most of these were actually diabetic radiculoplexopathies in which the femoral component dominated. They may represent an autoimmune process, perhaps with a vasculitic component. Vasculitis, such as polyarteritis nodosa, may manifest as mono­ neuritis multiplex, with acute involvement of the femoral nerve. Femoral neuropathies occasionally follow prolonged surger­ ies or childbirth in the lithotomy position, presumably from anatomic predisposition to kinking beneath the inguinal ligament. Iliacus hematoma or abscess, misplaced attempts at femoral artery or vein puncture, or iatrogenic injury after nephrectomy or hip arthroplasty are other recognized causes. Tumors, benign and malignant, may rarely cause femoral neu­ ropathy (Fig. 66-6). Isolated saphenous nerve injuries may result from knee arthroscopy, femoral–popliteal artery bypass surgery, and in the course of coronary artery bypass graft surgery.

CLINICAL PRESENTATION When the more proximal femoral nerve is involved, weakness of the iliopsoas manifests as limited hip flexion. Mild hip flexion weakness may also occur with more distal femoral nerve involve­ ment from poor function of the rectus femoris, the only head of the quadriceps muscle originating within the pelvis and con­ tributing to hip flexion. Patients with severe quadriceps weak­ ness are unable to extend the leg or lock the knee; when severe, this often interferes with or precludes walking. Initially, mild



CHAPTER 66  •  Mononeuropathies of the Lower Extremities  623

Lateral femoral cutaneous nerve Femoral nerve Obturator nerve

T12 L1 L2 L3 L4

Lumbar plexus

Lumbosacral trunk

lliacus muscle Psoas major muscle (lower part) Articular twig Sartorius muscle (divided)

Lateral femoral cutaneous nerve

Quadriceps femoris

Pectineus muscle Rectus femoris muscle (divided) Vastus intermedius muscle Vastus medialis muscle

Anterior cutaneous branches of femoral nerve Sartorius muscle (divided) Saphenous nerve

Vastus lateralis muscle Articularis genus muscle

Infrapatellar branch of saphenous nerve Medial crural cutaneous branches of saphenous nerve

Note: Only muscles innervated by the femoral nerve are shown.

Cutaneous innervation

Figure 66-5  Femoral Nerve and Lateral Cutaneous Nerve of Thigh.

thigh, and medial lower leg. A pure motor syndrome with quad­ riceps weakness and atrophy can result from lesions distal to the branching of the saphenous nerve in the thigh.

DIFFERENTIAL DIAGNOSIS A nerve root lesion at L3–L4 is the most common consideration. Unlike L5–S1 radiculopathies, a herniated nucleus pulposus infrequently involves the level L3–L4. Lumbosacral plexus lesions primarily affecting the lumbar nerves may also mimic femoral neuropathies.

LATERAL FEMORAL CUTANEOUS NEUROPATHY Figure 66-6  Femoral Nerve Neurofibromas in Neurofibromatosis (arrows).

femoral neuropathies may present with difficulty going down stairs because the knee buckles from mild quadriceps weakness. Eversion of the thigh might be impaired because of sartorius weakness. The patellar muscle stretch reflex is almost always diminished or absent in femoral neuropathies. Groin and thigh pain are frequent presenting symptoms. When patients experi­ ence sensory symptoms, these typically involve the anteromedial

Clinical Vignette A 38-year-old woman presented with pain and numbness of the left thigh in her seventh month of pregnancy. She described a burning discomfort extending from the hip to the lateral aspect of the thigh, intensified by standing or walking. There was associated cutaneous hypersensitivity with an aversion to having clothes or bed sheets rub against her. She was unaware of any other precipitating events. Examination demonstrated an elliptically shaped area of

624  SECTION XV  •  Mononeuropathies

sensory loss on the distal half of the left anterolateral thigh. She had no atrophy, weakness, or reflex loss. The symptoms gradually improved in the months following the delivery of a healthy baby.

The lateral femoral cutaneous nerve (LFCN) arises from the second and third lumbar roots and travels through the retro­ peritoneum. After traversing the psoas muscle, the nerve reaches the iliacus muscle (see Fig. 66-4). Medial to the anterior supe­ rior iliac spine, it exits the pelvis under or through the inguinal ligament, the presumed usual site of entrapment. Subsequently, it supplies sensation to the anterolateral thigh.

ETIOLOGY Meralgia paresthetica is an entrapment mononeuropathy of the lateral femoral cutaneous nerve (Fig. 66-7). Cadaver studies suggest that meralgia paresthetica is primarily an entrapment neuropathy due to “kinking” of the nerve as it passes through the inguinal ligament. Like many mononeuropathies, it is more common in people with diabetes. Meralgia paresthetica often occurs in overweight individuals, especially after sudden gain in weight, or in individuals wearing tight belts and garments. It is usually unilateral. Occasionally, the nerve is injured within the thigh secondary to blunt or penetrating trauma (e.g., a misplaced injection), or rarely, by a soft tissue sarcoma within the thigh.

Entrapment of nerve under inguinal ligament

Numbness and dysesthesias in lateral thigh

Figure 66-7  Lateral Femoral Cutaneous Nerve.

CLINICAL PRESENTATION Often aggravated by standing or walking, symptoms include an uncomfortable positive component (burning, hypersensitivity) and negative features (numbness). Typically, the area of demon­ strable sensory loss on examination is smaller than the lateral femoral cutaneous nerve territory in most anatomic diagrams, likely due to significant overlap with adjacent nerves. Because the LCFN is a purely sensory nerve, there are no associated reflex or motor abnormalities, helping to distinguish meralgia from other disorders that deserve diagnostic consideration.

DIFFERENTIAL DIAGNOSIS Although uncommon, L2 radiculopathy of any etiology, evidenced as weakness and denervation of L2-innervated hip flexors and adductors, is a differential consideration. Sensory symptoms and signs extend over the anterior and medial aspects of the thigh. Lumbar spinal stenosis also tends to be exacerbated by prolonged standing or walking, although it does not cause numbness in this specific distribution. Disorders of the lumbosacral plexus may mimic meralgia, particularly in patients having insidious onset of invasive or compressive disorders in which pain and other sensory symp­ toms have no obvious motor component. Retroperitoneal neo­ plasms or hematomas and abdominal surgery might affect the LCFN; however, they are unlikely to cause isolated meralgia. Instead, concomitant involvement of adjacent nerves usually leads to widespread motor, reflex, and sensory loss, indicating that there may be a plexus lesion rather than a single nerve problem. Isolated femoral neuropathies are uncommon and unlikely to be confused with meralgia because of the type and distribution of abnormalities. Sensory symptoms involve the anterior and medial thigh and extend to the medial surface of the leg. Weak­ ness of the quadriceps muscle and loss of its stretch reflex are other objective and distinguishing features. Although the LFCN can be tested by nerve conduction studies in the thigh distal to the inguinal ligament, technical difficulties interfere with detection of mild demyelinating inju­ ries. A response cannot be obtained from all individuals and is particularly difficult to record in overweight individuals who are most susceptible to this syndrome. Nerve conduction studies of the LFCN are of greatest value when a normal response is readily obtained from the asymptomatic side and a lowamplitude or absent response is obtained from the symptomatic side. In patients with atypical symptoms, thigh MRI is indicated to exclude primary lesions such as soft tissue sarcoma. MRI and CT of the retroperitoneum and pelvis should be considered in patients with unexplained LFCN neuropathy. Fasting blood glucose measurement is appropriate in acute-onset, painful LFCN neuropathies without alternative explanation.

MANAGEMENT The natural history of meralgia varies, but most patients become asymptomatic within 2 years. Others have a more protracted and chronic course. Conservative management includes weight loss and avoidance of tight garments. Medications such as



CHAPTER 66  •  Mononeuropathies of the Lower Extremities  625

amitriptyline, carbamazepine, gabapentin, and venlafaxine may diminish pain intensity. Injections of local anesthetics and ste­ roids near the anterior superior iliac spine may serve diagnostic and therapeutic roles and are sometimes “curative.” Exploration at the presumed entrapment site is used in particularly intrac­ table and lifestyle-altering cases.

gracilis muscles, whereas its terminal branch provides sensation to the distal medial thigh. The posterior division innervates the obturator externus, the superior portion of the adductor magnus, and sometimes the adductor brevis.

ETIOLOGY Obturator neuropathies may be caused by pelvic masses, diffi­ cult parturition, or obturator hernias or may be complications of hip arthroplasty or pelvic surgery.

OBTURATOR NEUROPATHIES Clinical Vignette

CLINICAL PRESENTATION

A 35-year-old woman presented with pain in the right medial thigh and difficulty walking. This had begun 6 months prior, immediately after the delivery of her son. After 8 hours of labor complicated by fetal failure to progress, she had eventually undergone an emergent cesarean section. On neurologic examination she had weakness of the right thigh adductors and a patch of numbness and dysesthesia on the medial surface of the thigh.

Obturator neuropathies are exceedingly uncommon focal nerve lesions that typically present with hip instability. Weakness and denervation are confined to the large hip adductors. Occasion­ ally, they present with pain and sensory symptoms in the medial thigh without obvious weakness.

The obturator nerve originates from the anterior rami of the L2, L3, and L4 nerve roots (Fig. 66-8). After its course through the pelvis, the nerve exits through the obturator canal and separates into the anterior and posterior divisions. The anterior division supplies the adductor longus, adductor brevis and

lliohypogastric nerve llioinguinal nerve Genitofemoral nerve

ILIOHYPOGASTRIC, ILIOINGUINAL, AND GENITOFEMORAL NEUROPATHIES These mononeuropathies should be considered in the differen­ tial diagnosis of dysesthesias of the pelvis and groin without apparent motor deficits. L1 L2 Lumbar plexus L3 L4 Lumbosacral trunk

Lateral femoral cutaneous nerve Femoral nerve Obturator nerve Posterior branch Articular branch Anterior branch Posterior branch Cutaneous branch Articular branch to knee joint Hiatus of adductor canal

Note: Only muscles innervated by the obturator nerve are shown.

Figure 66-8  Obturator Nerve.

Obturator externus muscle Adductor brevis muscle Adductor longus muscle (divided) Adductor magnus muscle (partly supplied by sciatic nerve) Gracilis muscle

Cutaneous innervation

626  SECTION XV  •  Mononeuropathies

ILIOHYPOGASTRIC NERVE The iliohypogastric nerve arises from the T12–L1 nerve roots. Like the ilioinguinal nerve, it supplies the internal oblique and transversus abdominis muscles. Weakness of these muscles, however, is difficult to demonstrate on physical examination. The iliohypogastric nerve divides in lateral and anterior cutane­ ous branches. Iliohypogastric neuropathies thus produce sensory symptoms in two distinct areas, the lateral aspect of the iliac crest and the suprapubic region. The anterior branch is most commonly injured by lower abdominal surgery with a lateral incision site extending to the internal oblique muscle, and the lateral branch is most commonly injured by major pelvic surgery. The prognosis for recovery is generally good in both.

ILIOINGUINAL NERVE This nerve arises from the L1 nerve root. Loss of sensation along the inguinal ligament, over the pubic symphysis and the anterior scrotum or mons pubis, with or without associated pain, characterizes ilioinguinal neuropathies. Ilioinguinal neuropa­ thies most frequently result from lower abdominal surgeries, bone graft harvesting from the iliac crest, and parturition. Rarely, nerve entrapment occurs as it passes through the abdominal wall, causing groin pain relieved by hip flexion.

GENITOFEMORAL NERVE The genitofemoral nerve is supplied by fibers originating from the L1 and L2 nerve roots. It separates into genital and femoral branches. Genitofemoral neuropathy presents with pain, numb­ ness, and paresthesias of the labia majora or scrotum as well as the proximal anterior thigh, lateral to the sensory territory of the ilioinguinal nerve. Standing or hip extension may exaggerate symptoms. Surgical procedures such as inguinal herniorrhaphies or appendectomies are common causes of genitofemoral neu­ ropathy. The genitofemoral nerve has a motor branch innervat­ ing the cremaster muscle. Unfortunately, the cremasteric reflex is not a reliable diagnostic clue.

DIAGNOSIS As the sensory territories of these three nerves overlap, their mononeuropathies are difficult to distinguish by clinical exami­ nation alone. The ilioinguinal, iliohypogastric, and genitofemo­ ral nerves are inaccessible to nerve conduction techniques. Therefore, EMG is of limited value and mainly serves the purpose to rule out differential diagnoses, such as L1 or L2 radiculopathies or proximal lumbar plexopathies. Local injec­ tions of anesthetics not only provide symptomatic relief but may also be diagnostically helpful. Retroperitoneal and pelvic MRI and CT are indicated when a progressive ilioinguinal, iliohypo­ gastric, or genitofemoral neuropathy develops without obvious cause.

MANAGEMENT Most patients with postoperative neuropathies experience full recovery; persistent symptoms typically are seen only in those

with unrepaired nerve transection or injury to the lumbosacral plexus. Medications such as amitriptyline, carbamazepine, gabapentin, and venlafaxine may diminish pain intensity in all mononeuropathies.

DIAGNOSTIC APPROACH TO MONONEUROPATHIES Electrodiagnosis is a primary means of assessing a suspected mononeuropathy. EMG helps to differentiate other lesions that mimic mononeuropathies, particularly at the respective plexus or nerve root level. Besides providing anatomic localization, EMG helps to assess prognosis. A specific etiology is rarely revealed, even with abnormal EMG. Demonstration of a pre­ dominantly demyelinating lesion provides the primary basis for localization, but this is generally not possible in sciatic, femoral, and obturator neuropathies, as conduction studies of these nerves are limited by technical factors. Further testing is sometimes indicated, depending on the index of suspicion regarding causation. Plain radiographs can assess possible bone spurs or exostoses, arthritides, congenital deformities, fractures, or bony tumors that may contribute to nerve injury. MRI and occasionally ultrasonography are useful in assessing soft tissue lesions or sometimes localizing areas of entrapment and in providing a spatial image of the nerve and its surrounding structures. However, when EMG indicates a defined localization without clinical evidence or imaging studies of a specific mechanism, surgical exploration is an important diagnostic tool that sometimes also offers a therapeutic option. Acute axonal nerve lesions are characterized by a hyperintense signal on T2-weighted MRI. Thus, MRI can demonstrate the site of nerve injury when localization by EMG is difficult. Fur­ thermore, MRI might be able to identify traumatic nerve lesions with the potential of axonal regeneration, and unnecessary sur­ gical explorations could be avoided. Occasionally, an elevated ESR provides a clue to an underlying vasculitis. Fasting serum glucose levels may help to identify previously undiagnosed diabetes mellitus presenting with a possible femoral neuropa­ thy. Rarely, CSF examination is indicated to distinguish an inflammatory or carcinomatous polyradiculopathy from a mononeuropathy.

MANAGEMENT AND PROGNOSIS OF MONONEUROPATHIES When a definable entrapment mechanism, a mass causing nerve compression, or a nerve laceration exists, surgery is indicated. If the neuropathy resulted from nerve traction from excessive squatting or compression from habitual leg crossing, the primary treatment is discontinuation of these activities. If a cast or brace is compressing the nerve, for example the peroneal nerve at the fibular head, it must be modified to protect the nerve. Nerve injury from an acute compartment syndrome is a surgical emergency and necessitates fasciotomy. Foot drop can be effectively treated by an ankle–foot ortho­ sis, its primary goal being the prevention of falls. Patients also state that their walking endurance improves with this device. An ankle–foot orthosis should be prescribed cautiously in patients with significant quadriceps weakness. It may destabilize a



CHAPTER 66  •  Mononeuropathies of the Lower Extremities  627

patient’s marginally compensated technique of “knee locking” and weight bearing, thus increasing the risk of falling. Recovery depends on the nature, location, severity, and per­ sistence of the injury and patients’ underlying health and age. An optimistic prognosis can be expected with a primary demy­ elinating lesion. Demyelinating lesions secondary to monopha­ sic external compression or stretch typically recover within weeks to months. However, when evidence of significant axonal damage exists, reinnervation, a process that progresses at a rate of 1 mm/day or approximately 1 inch/month, must occur. A longer period (months to years) is therefore required. The degree of axon loss and distance from the site of injury to the target site of reinnervation determine outcome.

synthetic or natural materials are being studied as scaffolds in lieu of nerve grafts and can deliver nerve growth factors. Laser phototherapy has been shown to promote nerve regeneration and is used for pain relief. Stem cell and progenitor cell dif­ ferentiation might also offer treatment options in the future.

FUTURE DIRECTIONS Future directions will involve improved diagnosis through more sensitive neurophysiologic and neuroimaging techniques, and more effective nerve repair and treatment of neuropathic pain. Despite improved surgical techniques, functional outcome after severe traumatic nerve injuries is often unsatisfactory. Auto­ grafts serve to bridge nerve gaps with limited success. An under­ standing of the molecular mechanisms of axonal regeneration including the role of Schwann cells, growth factors, and the extracellular environment is essential for the development of better treatment options. Nerve conduits manufactured from

ADDITIONAL RESOURCES American Association of Neuromuscular and Electrodiagnostic Medicine. Available at: http://www.aanem.org. Accessed July 6, 2008. The information on this website includes a list of suggested reading for physicians as well as educational material for patients with various neuromuscular disorders. Dumitru D, Amato A, Zwarts M. Electrodiagnostic Medicine. 2nd ed. Philadelphia, PA: Hanley&Belfus; 2002. This textbook is an excellent reference for physicians interested in disorders of the peripheral nervous system and electrophysiological techniques. Katirji B. Peroneal neuropathy. Neurol Clin 1999;17:567-591. The author provides a good review of the clinical presentation and electrophysiology of peroneal nerve lesions. Kuntzer T, van Melle G, Regli F. Clinical and prognostic features in uni­ lateral femoral neuropathies. Muscle Nerve 1997;20:205-211. This article studies the clinical and electrodiagnostic features influencing outcome in 32 patients with femoral neuropathy. Sorenson EJ, Chen JJ, Daube JR. Obturator neuropathy: causes and outcome. Muscle Nerve 2002;25:605-607. The authors retrospectively examine the causes and prognoses of obturator neuropathy in 22 patients. Sunderland S. Nerves and Nerve Injuries. 2nd ed. Edinburgh, Scotland: Churchill Livingstone; 1978. This outstanding textbook provides a detailed description of the anatomy and physiology of peripheral nerves and outlines the various mechanisms of nerve injury in great depth.

Amyotrophic Lateral Sclerosis James A. Russell

Clinical Vignette A 62-year-old female first noted difficulty walking over uneven ground. Progressive painless weakness developed over the course of the next 6 months; initially this affected the left leg more than the right, resulting in a number of falls. By the time she was evaluated by a neurologist, she could no longer cut her own food or clip her own finger nails. She denied any pain, sensory disturbance or change in her ability to think, speak, swallow, or breathe.

H

er examination revealed normal cognitive function. Cranial nerve examination revealed mild dysarthria, tongue fasciculations, the presence of a jaw jerk, and weakness of neck flexion. All limb muscles were weak, left more than right, more pronounced distally. Intrinsic hand muscles were atrophic. Fasciculations were noted throughout her limbs. Muscle stretch reflexes were brisk despite her weakness and atrophy. Plantar responses were extensor. Sensory examination revealed no abnormalities. In 1874, Jean-Martin Charcot described a disorder that he named amyotrophic lateral sclerosis (ALS). In France, it is referred to as Charcot disease, whereas motor neuron disease (MND) is the preferred name for the disorder in the United Kingdom. In the United States, ALS is better known as Lou Gehrig’s disease. Charcot’s description was of a disorder characterized by loss of voluntary motor function, resulting from degeneration of anterior horn cells, corticospinal tracts, and motor cranial nerve nuclei and cortical motor neurons (Figs. 67-1 and 67-2). ALS is a sporadic disorder (sALS) in the majority of cases. ALS is inherited in 5–10% of cases, i.e., familial ALS (fALS), usually in an autosomal dominant fashion. In general, fALS patients have phenotypes that closely resemble sALS, although fALS may have an earlier onset. In absence of family history, the disorders are clinically indistinguishable. The incidence of ALS approximates 1.8 in 100,000. The incidence of ALS in men is twice that in women, although this ratio becomes closer to 1 : 1 in a postmenopausal population. The median age at onset is 55 years of age; this disease may afflict patients in their late teens or in their 90s. The average life expectancy is between 2 and 3 years; in less than 10% of patients, ventilator-independent survival of less than 1 year or greater than 10 years is seen. Half of affected individuals die within 3 years and only a quarter survive 5 years without dependency on invasive mechanical ventilation. Young males and patients with restricted upper motor neuron (UMN) or lower motor neuron (LMN) presentations tend to have a slower course. Primary bulbar (disordered speech and swallowing) presentations tend to disproportionately affect older women and appear to have a more rapid course.

67 

In the United States, it is estimated that at any given time 25,000 patients are diagnosed with ALS. The prevalence of ALS appears to be increasing, perhaps because of an aging population. Other than historical observations identifying an increased incidence on Guam and the Kii peninsula of Japan, there does not appear to be any particular geographic location or ethnic group that has a significantly higher risk of contracting ALS.

ETIOLOGY, GENETICS, AND PATHOGENESIS The cause of sporadic ALS is unknown. As with other neurodegenerative diseases, it is hypothesized that ALS may result from the dual insult of genetic susceptibility and environmental injury. Attempts to identify predisposing mutations and potential toxic or infectious agents have been unsuccessful to date. It has been long recognized that a small percentage of patients (fALS) have an autosomal dominant pattern of Mendelian inheritance. A major breakthrough in our understanding of familial ALS took place in 1991 with the identification of cytosolic copper-zinc superoxide dismutase (SOD1) gene mutations on chromosome 21q22.11 in affected individuals in some families. This represents the most frequently identified form of fALS. SOD1 is a free radical scavenger. Recognition of the SOD1 mutation led to the hypothesis that SOD1-fALS was mediated by free radical toxicity. However, SOD1 knock-out mouse with no SOD1 protein do not develop motor neuron disease. In contrast, heterozygote mice become symptomatic and die from a paralyzing disorder. It is thought that SOD1 mutations may injure neurons through conformational changes in the SOD1 protein. Particularly intriguing has been the recognition of the phenotypic heterogeneity in SOD1 fALS (Table 67-1). About 114 pathologic mutations have been identified within the five exons of the SOD1 gene; each of these mutations may produce a distinct phenotype. The most common mutation found in North America is an alanine for valine (A4V) substitution at codon 4; this typically produces a lower motor neuron dominant phenotype (LMN-D) with a life expectancy approximating 1 year. Table 67-1 summarizes the phenotypic heterogeneity that results from different SOD1 mutations. SOD1 mutations are not fully penetrant. It is estimated that individuals carrying the mutation have an 80% chance of developing disease by age 85 years. SOD1 mutations constitute 20–25% of all individuals with fALS. Other fALS genotypes are listed in Table 67-2. Some of these mutations produce a predominantly lower motor neuron (LMN) or upper motor neuron (UMN) disorder and more closely resemble the phenotypes of spinal muscular atrophy or hereditary spastic paraparesis, respectively. Mutations that may produce both a frontotemporal lobar degeneration and motor neuron disease occur on chromosomes 9p13.2-21.3, 9q21-q22, and 17q21. A recently identified fALS mutation occurs in the TAR DNA-binding protein, 43

Cerebral Cortex: Efferent Pathways 6

8

4 31 2

19

From frontal cortex to thalamus, basal ganglia, pontine nuclei, and reticular formation

18

41 42

17

From parietal cortex to thalamus, pontine nuclei, and reticular formation Thalamus Posterior limb of internal capsule

Corticobulbar, corticorubral, corticonuclear, and corticospinal pathways Caudate nucleus Anterior limb of internal capsule Lentiform nucleus Globus pallidus Putamen

From occipital eye fields to superior colliculus From auditory cortex to inferior colliculus Superior colliculi Interstitial nucleus of Cajal Inferior colliculus

From frontal eye fields to interstitial nucleus of Cajal Cerebral peduncle Red nucleus

Trigeminal sensory nucleus Trigeminal motor nucleus Reticular formation

Corticospinal axons Corticonuclear axons Pons For pontocerebellar connections

Solitary tract nucleus Nucleus ambiguus Dorsal motor nucleus of vagus and glossopharyngeal nerves

Facial nerve nucleus of opposite side for lower face

Hypoglossal nucleus Reticular formation

Upper part of medulla oblongata Pyramids

Cuneate nucleus Gracile nucleus Reticular formation

Lower part of medulla oblongata Decussation of pyramids

Lateral (crossed) corticospinal tract

Anterior (direct) corticospinal tract

Posterior (dorsal) horn

Spinal cord Anterior (ventral) horns

AWC

Figure 67-1  Cerebral Cortex: Efferent Pathways.

Area 6

Area 4

Hip Trunk

Primary motor cortex (Area 4)

Arm Neck

Hand e Fac

Brow Eyelid Nares

Lateral aspect of cerebral cortex to show topographic projection of motor centers on precentral gyrus and premotor and supplemental motor cortex

Lips Tongue

Posterior limb

Larynx

Internal capsule Anterior limb III

IV (ipsilateral and contralateral)

IV

VI

VI

Pons

III (ipsilateral and contralateral)

III

IV

Midbrain

V

VI

V

VII upper VII lower

V

VII to upper face (ipsilateral and contralateral) VII to lower face (contralateral only)

Upper Lower VII

Medulla

XII

Nucleus ambiguus (IX, X, XI)

VII

XII (ipsilateral and contralateral)

XII XII

IX, X, XI

Figure 67-2  Corticobulbar Fibers.

VI (ipsilateral and contralateral) V (ipsilateral and contralateral)

IX, X, XI

IX, X, and XI (ipsilateral and contralateral)

632  SECTION XVI  •  Motor Neuron Disorders

(TDP-43) gene. Non-amyloid, structurally modified TDP-43 has been recognized as a major constituent of the ubiquitinated inclusions found in cortical neurons of patients with both sporadic (s) and familial (f) forms of frontotemporal lobar degeneration (FTD). There are many proposed mechanisms for motor neuron death in sALS, including excitotoxicity secondary to glutamate, free radical–mediated oxidative cytotoxicity, mitochondrial dysfunction, protein aggregation, cytoskeletal abnormalities, aberrant activation of cyclo-oxygenase, impaired axonal transport, activation of inflammatory cascades, and apoptosis. Why the motor neurons and corticospinal/bulbar tracts are vulnerable in a selective manner remains unknown. Why the disease begins focally and progresses in a regional fashion is also unknown. One putative hypothesis is that misfolded, toxic protein aggregates may proselytize normal protein in adjacent neurons, analogous to mechanisms proposed for prion diseases. Table 67-1  Phenotypic Variation in SOD1 fALS Phenotype

SOD 1 Mutation

Lower motor neuron predominant Upper motor neuron predominant Slow progression (>10-year survival)

A4V, L84V, D101N D90A G37R, G41D, G93C, L144S, L144F A4T, N86S, L106V, V148G G85R, H46R G37R, L38V G41D V148I D90A, I113T E100G

Fast progression (35 CAGs) in the androgen receptor (AR) gene.

M

otor neuron diseases (MNDs) are disorders that produce painless weakness, atrophy, cramps, and fasciculations and are consequent to degeneration of anterior horn cells and selective cranial nerve nuclei. This chapter will address notable MNDs other than ALS. Many of the disorders discussed in this chapter have known or suspected genetic mechanisms. The spinal muscular atrophies (SMAs) are conceptualized as largely inherited disorders in which there is predominant degeneration of anterior horn cells and selective cranial nerve nuclei. In the childhood SMAs, mutations of a single gene and derangement of a single gene product are responsible for the majority of cases, and the resultant phenotype is fairly homogeneous. In other disorders, for example, hereditary spastic paraplegia (HSP), there are a plethora of recognized genotypes correlating with an almost equally heterogeneous array of phenotypic variations.

68 

Because of the relative rarity of these disorders, societal impact is usually limited. However, as with most hereditary disorders, the impact on individuals and families is substantial. This is particularly true for spinal muscular atrophy type I where parents have to cope with the consequences of a newborn with a lethal illness as well as with the specter that subsequent children are at risk. SMA I, also known as Werdnig–Hoffman disease, is the most common of the SMAs. Its incidence is estimated to be between 4 and 10 in 100,000 live births depending on the geographic cohort studied. After cystic fibrosis, it is the second most common, lethal, recessively inherited disorder of Caucasians.

CLINICAL PRESENTATION Spinal Muscular Atrophy Types I–IV Spinal muscular atrophy types I–IV are allelic disorders of the survival motor neuron (SMN) gene 1 located on chromosome 5q12.2-q13.3. When there is more than one affected individual in a given family, the phenotype is typically homogeneous but may be disparate in some cases. In normal individuals, there are two copies each of the SMN1 and SMN2 genes. Both genes produce similar but not identical proteins; the SMN2 gene appears to produce an unstable and rapidly degrading protein that can partially compensate for the lack of the SMN1 protein. There are no known clinical consequences from mutations of the SMN2 gene alone. It is estimated that 95% of SMA I–III patients are homozygous for deletion of exons 7 and 8 of the SMN1 gene. The remainder are thought to be compound heterozygotes with absence of exons 7 and 8 on one allele and a point mutation of the other SMN1 allele. The severity of the SMA phenotype appears to be related to the number of SMN2 copies available to compensate for deleted SMN1 gene. Homozygotes devoid of SMN1 who harbor two copies of SMN2 tend to manifest as an SMA I phenotype. An increasing number of SMN2 copies correlates with proportionately milder (SMA II-IV) forms of the disease. Individuals homozygous for the SMN1 mutation with five copies of the SMN2 gene have been reported to be asymptomatic. Why motor neurons remain selectively vulnerable to SMN deficiency remains unknown. Of the multiple SMA phenotypes, the infantile and childhood forms are the most prevalent. SMA type I or Werdnig– Hoffman disease is the most severe form (Fig. 68-1). Clinical manifestations become evident within the first 6 months of life. In contrast to the latter three categories, afflicted children with SMA I never develop the capability of sitting independently. In some cases, recognition of reduced movement occurs in utero or within the first few days of life. Affected infants are hypotonic with a symmetric, generalized, or proximally predominant

642  SECTION XVI  •  Motor Neuron Disorders

Muscle biopsy specimen showing groups of small atrophic muscle fibers and areas of normal or enlarged fibers (group atrophy) (trichrome stain).

Baseline tremor in otherwise normal electrocardiogram Electromyography (motor units during active contraction)

Normal Infant with typical bell-shaped thorax, frog-leg posture, and “jug-handle” position of upper limbs

Boy with much milder, late-onset form of disease (Kugelberg-Welander disease). Marked lordosis and eversion of feet

Werdnig-Hoffman disease Figure 68-1  Spinal Muscular Atrophy Type 1.

pattern of weakness. Like ALS, facial weakness is typically mild and extraocular muscles are spared. Fasciculations are seen in the tongue but rarely in limb muscles, presumably because of the ample subcutaneous tissue of neonates. Manual tremor, so characteristic of SMA types II and III, is rarely present. Deep tendon reflexes are typically absent. Abdominal breathing, a weak cry, and a poor suck are commonplace. Ventilation difficulties stem primarily from intercostal rather than diaphragmatic weakness. Pectus excavatum and a diminished anteroposterior diameter of the chest are seen. Mild contractures may occur but arthrogryposis is not part of the classic phenotype. Intellectual development is normal. Without mechanical ventilation, death is inevitable, almost always within a year or two. An earlier age of onset correlates with a shorter life expectancy. SMA type Ia refers to a severe form of neonatal SMA associated with arthrogryposis multiplex congenita and a paucity of movement. Prognosis is poor with ventilatory support required at birth. The intermediate form or SMA II typically begins between 6 and 18 months of age. The disorder is clinically defined by a child who sits independently but never walks. Postural hand tremor is the only significant phenotypic variance from Werdnig–Hoffman disease. Tongue fasciculations, areflexia, and a generalized to proximally predominant and symmetric pattern of weakness mimic the SMA I phenotype. Approximately 98% of these individuals survive to age 5 and two thirds to age 25. In view of the more protracted course and of wheelchair

dependency SMA II and SMA III patients commonly acquire kyphoscoliosis and joint contractures (Fig. 68-2). The SMA III or the Kugelberg–Welander syndrome differs from the intermediate form only in the age of onset, milestones achieved, and life expectancy. Affected individuals develop the ability to stand and walk. Onset age is typically 18 months or more. Certain authors have attempted to divide SMA III into type a and type b, based on age at onset of symptoms, with the intention of better defining the natural history in individual patients. In SMA type IIIa, defined as symptom onset before 3 years, it is estimated that 70% will remain ambulatory 10 years after symptom onset. Twenty percent will still ambulate in 30 years after symptom onset. In SMA type IIIb, defined as symptom onset after 3 years, virtually all patients will remain ambulatory in 10 years and 60% at 40 years after symptom onset. Life expectancy extends into the sixth decade and may be normal in many individuals. Initial symptoms are typically related to proximal weakness. Hand tremor, areflexia, and tongue fasciculations are commonplace. Fascicu­ lations in limb muscles are more evident than in SMA types I and II. Adult-onset SMA IV is a rare, genetically heterogeneous disorder. SMA IV children achieve motor milestones at normal ages. Onset of weakness is typically in the third or fourth decade in the recessively inherited cases. Initial symptoms are typically proximal weakness of the lower extremities, particularly the hip flexors, hip extensors, and knee extensors. Shoulder abductors



CHAPTER 68  •  Other Motor Neuron Diseases and Motor Neuropathies  643

Posterior bulge of ribs on convex side forming characteristic rib hump in thoracic scoliosis Spinous process deviated to concave side Lamina thinner, vertebral canal narrower on concave side

Rib pushed posteriorly; thoracic cage narrowed

Vertebral body distorted toward convex side Rib pushed laterally and anteriorly Convex side Concave side Characteristic distortion of vertebra and rib in thoracic scoliosis (inferior view) Ribs close together on concave side of curve, widely separated on convex side. Vertebrae rotated with spinous processes and pedicles toward concavity.

Section through scoliotic vertebrae. Decreased vertebral height and disc thickness on concave side.

Figure 68-2  Pathologic Anatomy of Scoliosis.

and elbow extensors are the most frequently affected muscles of the arms. Tongue fasciculations, hand tremor, and in some cases, calf hypertrophy may occur. Life expectancy in SMA IV is normal. Parents with SMA IV have given birth to children with more severe SMA phenotypes.

Spinal Muscular Atrophy with Respiratory Distress (SMARD1) This is a rare disorder in which infants develop diaphragmatic weakness and ventilatory weakness in addition to hypotonia.

X-Linked Bulbospinal Muscular Atrophy (SBMA)—Kennedy Disease SBMA is an X-linked disorder associated with an androgen receptor gene mutation. Consequently, it has frequent endocrine as well as neuromuscular consequences, the latter providing the primary source of morbidity. SBMA is an X-linked, adult-onset disorder that is depicted in the vignette at the beginning of this chapter. It is a disorder almost exclusively of males with a median age of onset of 44 years. Initial symptoms are usually attributable to weakness of bulbar or proximal limb muscles. Younger men, and rarely female carriers, may be symptomatic but may go undiagnosed unless there are other previously diagnosed family members.

As the name implies, the clinical manifestations are largely referable to degeneration of the lower cranial nerve motor nuclei and anterior horn cells of the spinal cord. The weakness progresses insidiously and is proximally predominant and symmetric in pattern. Typically, symptoms referable to the lower extremities have the greatest initial impact. Approximately 10% of the time, the initial symptoms pertain to difficulty with swallowing, chewing, or speaking. Facial weakness is common. Jaw drop due to muscles of mastication may occur as well. Perioral and tongue fasciculations are common and represent helpful clinical clues. Like ALS, ptosis and ophthalmoparesis should suggest an alternative diagnosis. Like other SMAs, postural tremor is common. There is an associated, but frequently asymptomatic, sensory neuropathy that may only be recognized by nerve conduction studies. Clinical heterogeneity exists. Asymmetry of muscle weakness at onset has been emphasized by some authors. Occasionally, rapidly progressive weakness occurs. The median age of wheelchair dependency is 61 years or approximately 15 years after onset of weakness. Women who are heterozygous for Kennedy disease mutation may rarely be symptomatic. The effects of SBMA are not restricted to the neuromuscular system. Affected males suffer the consequences of androgen insensitivity, including gynecomastia, impotence, testicular atrophy, and potential infertility. There is also an increased incidence of diabetes mellitus.

644  SECTION XVI  •  Motor Neuron Disorders

Asymmetric atrophy of intrinsic hand muscles

A

B

A. and B. Sagittal T2 fast spin echo imaging of cervical spinal cord in

(A) neutral and (B) flexion. Note marked expansion of posterior epidural space on flexion with signal voids indicating enlarged veins. C, Atrophy of the forearm and intrinsic hand muscles (C7, C8, and T1 myotomes) in Hirayama disease with sparing of brachioradialis. Courtesy Dr. Devon Rubin, Mayo Clinic.

Asymmetric atrophy of forearm muscles with sparing of brachioradialis

C Figure 68-3  Hirayama Disease.

Juvenile Segmental Spinal Muscular Atrophy—Benign Focal Amyotrophy— Hirayama Disease Unlike other SMAs, Hirayama disease appears to be a sporadic disorder in the majority of cases. In 1963, Hirayama described a slowly progressive, focal motor neuron disease affecting one, and at times, both upper extremities. In this and subsequent descriptions, males are affected in 60% of cases. Hirayama disease is perhaps best considered as a segmental or regional form of spinal muscular atrophy. Onset is typically between ages 15 and 25 with a range of 2 to 30 years. Although most commonly reported in those of Asian origin, it may occur in any ethnic background. The characteristic phenotype is the insidious development of atrophy and weakness in C8–T1 muscles of the hand and forearm. It begins unilaterally, typically in the dominant extremity. Over the course of months to years, the weakness may gradually spread to involve more proximal muscles. In a third of cases, there is clinical weakness of the opposite limb. An even higher percentage will have bilateral upper extremity involvement on electrodiagnostic studies. Tendon reflexes in the involved limb may be spared, although neither overt pyramidal or bulbar involvement occurs. Reflex preservation may reflect the restricted nature of the disease and the lack of a reliable C8–T1 muscle stretch reflex. Like many other SMAs, tremor may occur. In most cases, there is an arrest of further progression after 6 years or less. Although a significant decline in

affected limb function in the cold is common with all motor neuron diseases, “cold paresis” is particularly emphasized in this population. Hyperhidrosis of the involved limb has been described. Hirayama disease is less frequently seen in Western populations. Ischemic changes in the cervical spinal cord of a single autopsied case of Hirayama disease led to the hypothesis of a compressive mechanism. In 2000, Hirayama reported the results of dynamic imaging in 73 patients and 20 controls. Ninety-four percent of patients had significant forward displacement and flattening of the posterior surface of the cervical cord during neck flexion (Fig. 68-3). The presumption is that the blood supply to the spinal cord is compromised, with the anterior horn representing the watershed and the most susceptible to ischemia. Other observations that supported this potential mechanism are the frequent asymmetric nature of spinal cord flattening in keeping with the asymmetric disease onset, and the lesser degree to which distortion occurred in older patients in whom progression had arrested. Nonetheless, this pathogenetic hypothesis is not universally accepted.

Scapuloperoneal Form of SMA (Davidenkow Disease) A scapuloperoneal pattern of weakness may result from either neurogenic or myopathic disorders. The neurogenic form of the scapuloperoneal syndrome has been referred to by the eponym



CHAPTER 68  •  Other Motor Neuron Diseases and Motor Neuropathies  645

Table 68-1  Genetics of Spinal Muscular Atrophies Classification

Chromosome

Gene

SMA I-IV SMARD I SBMA (Kennedy) Juvenile segmental SMA (Hirayama) Scapuloperoneal (Davidenkow)

5q12.2-q13.3 11q13.2-q13.4 X None identified

SMN1 IGHMBP2 Androgen receptor gene None identified

17p11.2

PMP 22

Davidenkow disease. It has been considered to represent a SMA variant even though distal sensory loss was common in Davidenkow’s original series. Symptomatic onset typically occurs in late childhood related to asymmetric weakness of scapular fixators or foot dorsiflexors. Weakness typically progresses into a more generalized pattern. Some patients with a neurogenic scapuloperoneal syndrome have been found to have mutations within the PMP-22 gene. This suggests that the disorder might be more correctly characterized as a hereditary neuropathy.

Distal SMA (Hereditary Motor Neuronopathy, Spinal Forms of Charcot– Marie–Tooth Disease) Distal SMA (dSMA) is usually inherited in a dominant fashion in one third of cases but may have recessive or X-linked pattern as well. There are numerous genetic loci (Table 68-1). Like hereditary spastic paraparesis, distal SMA can be either “pure” or “complicated” based upon other neurologic system involvement. Complicated phenotypes may include diaphragmatic paralysis, vocal cord paralysis, and arthrogryposis. Harding and Thomas introduced the concept of dSMA in 1980. The dSMAs have been perceived as progressive, hereditary disorders producing distal symmetric weakness in the absence of either clinical or electrodiagnostic sensory loss. The dSMAs have also been referred to as hereditary motor neuropathies but are considered to be anterior horn cell disorders in view of their pure motor manifestations. Distal SMA strongly resembles Charcot–Marie–Tooth (CMT) disease without sensory involvement. In fact, at least three forms of dSMA are allelic to recessively inherited forms of CMT. Weakness in distal SMA typically predominates in ankle dorsiflexors and evertors and toe extensors. Foot deformities characteristic of CMT are also common. Hand muscles may eventually become involved. There are a number of recognized dSMA genotypes (see Table 68-1).

Poliomyelitis Poliomyelitis is a viral infection with tropism for gray matter of the spinal cord and motor cranial nuclei. Poliomyelitis translates literally into inflammation of spinal cord gray matter. It is often used synonymously with paralytic polio caused by the polio virus. In this chapter, it will refer to any viral infection with a predilection for anterior horn cells or motor cranial nerve

nuclei. Polio may be either a monophasic or biphasic disease. The initial symptoms are nonspecific, last 1–2 days, and are predominantly constitutional and/or gastrointestinal in nature. They consist of fever, malaise, pharyngitis, headache, nausea, vomiting, and abdominal cramping (Fig. 68-4). In the majority of infected individuals, the illness is self-limited and ends at this point. In individuals who fall victim to the “major” illness, symptoms of brain or spinal cord involvement develop 3 to 10 days subsequent to the initial symptoms. The major illness is defined by CNS involvement with meningoencephalitis, with or without an associated paralytic component. Stiff neck, back pain, and fever are prominent; encephalitis with altered mental status can also be seen. In individuals destined to develop paralytic disease, myalgias and cramping rapidly evolve into muscle weakness. The progression reaches its nadir within 48 hours of onset. The paralysis is typically asymmetric. It is confined to the limbs and trunk in half of the cases. There is a predilection for lumbosacral segments and proximal more than distal muscles (Fig. 68-5). Ten percent of cases have bulbar weakness only. Children are particularly susceptible to bulbar polio. Motor functions of the 7th, 9th and 10th cranial nerves are most likely to be affected. Ten percent of patients will manifest both spinal and bulbar weakness; ventilatory failure is more common in this group. Affected limbs are flaccid and areflexic. Like virtually all motor neuron disorders, the 3rd, 4th, and 6th cranial nerves are spared. Sensory signs and symptoms are atypical. In keeping with the known pathological involvement of the brainstem tegmentum and hypothalamus in cases with encephalitic components, clinical dysautonomia including fluctuating blood pressure, cardiac arrhythmia, and hyperhydrosis may occur. The natural history of paralytic polio is variable, dependent in large part on the severity and extent of the initial illness. As in GBS, less than 10% of individuals will die from the acute illness. Acute mortality typically results from ventilatory failure or the complications of immobility. Those who survive typically regain strength inversely proportionate to the severity of the initial illness. The majority of this recovery takes place over the course of weeks to months, presumably due to reinnervation from neighboring motor units not affected by the disease. The postpolio syndrome (PPS) has been recognized since 1875 but received no more than cursory attention until 1981 when interest escalated in response to the large numbers of people affected by the epidemics of the early 1940s who were now experiencing new symptoms. Current evidence suggests that patients who develop postpolio muscular atrophy do so because of the loss of anterior horn cells that occur as a consequence of normal aging superimposed upon a depleted reserve. There is convincing evidence that some individuals with prior polio may develop slowly progressive weakness (average decline 1%/year) after a protracted period of stability. How frequently this postpolio muscular atrophy (PPMA) occurs as a manifestation of PPS is a matter of some controversy. In one study, 50 prior polio patients were selected from a cohort of 300 patients and followed for 5 years. Sixty percent of this group developed symptoms. Of this symptomatic group, only a third had symptoms attributed to musculoskeletal complaints and none of these had measurable evidence of progressive atrophy and weakness. When PPMA occurs, it typically manifests in the regions most

646  SECTION XVI  •  Motor Neuron Disorders

Effects of live, attenuated poliovirus vaccine orally administered (OPV)

Hypothesis of pathogenesis Vaccine virus A. Virus is ingested by mouth. B. Only if amount of ingested virus is very large is there primary infection of oropharyngeal mucosa.

Antibody D. Varying amounts of virus enter bloodstream.

C. In most instances virus is swallowed and passes through stomach into intestine, where it multiplies rapidly and invades aggregated lymph nodules of intestinal wall (Peyer patches).

Extensive multiplication of vaccine strains in alimentary tract with minimal or no viremia results in resistance of alimentary tract to subsequent infection by naturally occurring polioviruses. Development of antibodies in blood that can neutralize naturally occurring polioviruses, which may escape barrier of resistant alimentary tract

Medulla oblongata Other susceptible extraneural tissues E. Other susceptible extraneural tissues, including oropharynx, are then frequently secondarily infected via bloodstream, and virus also multiplies there.

G. Virus is excreted in feces, by which it is disseminated.

Spinal cord F. From sites of multiplication in intestine, oropharynx, and other extraneural tissues, virus reaches central nervous system, probably via regional afferent neural pathways, first into motor neurons of spinal cord (primary spinal paralysis) or medulla (primary bulbar paralysis). Further axonal spread of virus then occurs along insulated tracts to distal neurons elsewhere in central nervous system, and also by contiguity to adjacent motor neurons.

Properly vaccinated persons have intestinal resistance to subsequent infection by naturally occurring polioviruses. Result is markedly decreased or no multiplication of these viruses in alimentary tract, which breaks chain of dissemination.

Paralytic poliomyelitis in USA, 1951 to 1976 (average number of cases per year) and effect of vaccine 1951-1955

No vaccine plus IPV* 1955

1956-1960

IPV only

1961-1965

IPV plus OPV† antiepidemic plus later community programs

1973-1976

OPV only

22,208 4594 468 9 (including imported and questionable cases)

*IPV  inactive poliovirus vaccine (Salk) †OPV  oral poliovirus vaccine (Sabin)

Figure 68-4  Pathogenesis of Poliomyelitis.

severely afflicted by the initial illness. Ventilatory function may decline, with one study suggesting an approximate 2% loss of vital capacity a year in keeping with the slowly progressive nature of the illness. Criteria have been established to solidify a PPMA diagnosis. These include objective measures of declining strength, muscle atrophy, and fatigue following a documented polio-like illness. This must occur subsequent to a protracted period of stability in absence of an alternative explanation.

There is no “gold standard” to determine which polio victims have developed PPMA. Consequently, estimates of the prevalence of PPS have ranged from 22 to 85%. Signs and symptoms of PPS have been reported to begin as early as 8 years after the initial illness or as late as 71 years with an average of 35 years. The likelihood of developing PPS seems to correlate with both the age of the patient at the time of the initial illness, as well as its severity.



CHAPTER 68  •  Other Motor Neuron Diseases and Motor Neuropathies  647

Stages in destruction of a motor neuron by poliovirus

A. Normal motor neuron

B. Diffuse chromatolysis; three C. Polymorphonuclear cells acidophilic nuclear inclusions around nucleolus

invading necrotic neuron

D. Complete neuronophagia

Paralytic residua of spinal poliomyelitis Relative distribution of neuronal lesions in spinal and bulbar poliomyelitis

Multiple crippling deformities; contractures, atrophy, severe scoliosis and equinovarus

Medulla

Spinal

Cervical

Thoracic

Bulbar

Lumbar

Scoliosis Genu recurvatum, atrophy of limb

Figure 68-5  Poliomyelitis.

West Nile Virus West Nile virus (WNV) is a mosquito-borne viral pathogen of the Flavivirus family. Like polio, most infected individuals develop a minor, nonspecific illness that often includes fever, gastrointestinal complaints, back pain, and rash in addition to potential neurologic manifestations. A number of reports have linked WNV to a poliomyelitis-like phenotype that may affect facial as well as limb muscles with or without an associated meningo-encephalitic component. Approximately half of patients will develop flaccid weakness over a 3- to 8-day period that tends to be proximal and asymmetric in distribution. Electrophysiological and pathologic observations have suggested that this weakness originates from anterior horn cell injury. Confounding these observations are reports that the West Nile virus may produce Guillain–Barré and transverse myelitis phenotypes. Like the poliovirus, varying degrees of irreversible paralysis may result. Other agents that have been reported to cause poliomyelitis include enterovirus 71, acute hemorrhagic conjunctivitis, Coxsackie virus group A type 7, echovirus type 6, and the Japanese encephalitis virus. Rabies may also present as a paralytic illness in 20% of cases, with paralysis typically beginning in the bitten extremity.

Multifocal Motor Neuropathy The majority if not all of the evidence available to date suggests that multifocal motor neuropathy (MMN) is an immunemediated neuropathy resulting from multifocal myelin loss in

peripheral motor axons. This selective vulnerability hypothetically exists because of a glycolipid epitope that is unique to or predominantly found in the myelin of peripheral motor nerves. Although antiganglioside antibodies are found in the serum of 30–80% of individuals with the MMN phenotype, a pathogenetic role for these antibodies remains unproven. Reduction in antiganglioside antibody levels does not correlate with disease responsiveness in all patients. Conversely, patients with the MMN phenotype who are seronegative appear to respond equally well to immunomodulating treatments. MMN is characterized as a multifocal, pure motor, acquired immune mediated motor neuropathy. Despite this anatomic localization, it is more likely to be considered in the differential diagnosis of a motor neuron disease than a peripheral neuropathy. Like ALS it presents with painless weakness in a single limb, often in distal muscles in the upper extremity. Cramps and fasciculations may occur providing an additional phenotypic overlap with ALS. Like ALS, muscle stretch reflexes may be lost in an affected extremity. The clinical features that are most useful in distinguishing MMN from ALS include slower progression, the absence of unequivocal upper motor neuron signs, weakness without atrophy, nerve rather than segmental pattern of muscle weakness, and absence of signs attributable to cranial nerve dysfunction. The latter have been only reported as a rare consequence of MMN. Unfortunately with disease progression, these diagnostic clues may become obscured. On average, untreated MMN progresses much more slowly than ALS.

648  SECTION XVI  •  Motor Neuron Disorders

Hereditary Spastic Paraplegia There are in excess of 30 different gene mutations associated with the hereditary spastic paraplegia (HSP) phenotype. Autosomal dominant, recessive, and X-linked modes of transmission are recognized. The multiple genotypes underlying HSP suggest that there is a common mechanism by which mutations of different proteins translate into an identical or near-identical phenotype. A uniform final common pathway, however, is yet to be defined. Proposed mechanisms include disturbances in axon transport, impaired Golgi function, mitochondrial dysfunction, disordered myelin synthesis, and maturational disturbances of the corticospinal tracts. Some of these hypotheses are based upon the intracellular positioning of affected proteins. The pathology of HSP would support its conceptualization as a “dying back myelopathy.” HSP is a slowly progressive upper motor neuron (UMN) disorder of the lower extremities. Like other heritable disorders, other affected family members may not be readily identifiable. The presenting symptoms of HSP occur as a consequence of lower extremity spasticity that is symmetric in its distribution. Patients lose the ability to run or hop early in the course because of increased lower extremity extensor tone and the inability to flex the hip or knee in a facile manner. As a result, stride length is reduced. The legs tend to “scissor,” that is, cross over each other because of increased tone of thigh adductor muscles. Circumduction, that is, advancing the leg in a circular rather than a linear motion, is done for compensatory reasons to avoid tripping on a foot that maintains an inverted and plantar flexed posture. Leg strength may be diminished; weakness occurs in an “upper motor neuron” pattern, with hip flexors, knee flexors, and foot dorsiflexors being affected to the greatest extent. Hyperreflexia of the lower extremities is a universal feature, almost always accompanied by extensor plantar responses. Hyperreflexia of the upper extremities with Hoffman’s signs and reflex spread are common as well. Weakness, increased tone, impaired coordination or loss of function of the upper extremities, and cranial nerve dysfunction occur infrequently in pure HSP and should lead to consideration of an alternative diagnosis. Posterior column involvement with loss of vibratory sense in a length-dependent pattern in the lower extremities may be seen. Urinary frequency, urgency, and urgency incontinence are common symptoms even within the “pure” forms of the disease. Rectal urgency and incontinence and sexual dysfunction are less common but do occur. High arched feet and hammer toe deformities, a feature of a number of chronic neurologic diseases, are a common feature of the illness. Onset and severity of HSP varies considerably both within and between families. Initial symptoms may be recognized in any decade of life. The reasons for variations of disease onset and severity of affliction, both within and between families of the same genotype, are not currently understood although other “disease-modifying” genes are hypothesized to have a role.

Miscellaneous Causes of Motor Neuron Disease Motor neuron disease phenotypes have occurred in association with other disorders. Understandably, little is known of the

pathogenesis of these disparate and relatively uncommon disorders. Postirradiation neuropathy is frequently a pure motor syndrome; current evidence, including reports of root enhancement on MR imaging in some patients, favors a polyradiculopathy as the proposed pathomechanism. Radiation injury of the peripheral nervous system is typically delayed in onset with an average latency between exposure and symptoms of 6 years. The range, however, is exceedingly broad, with onset latency varying between 4 months and 25 years. Radiation doses typically exceed 4000 cGY in these patients. Motor neuron disease may rarely occur as a paraneoplastic disorder or as a potential complication in irradiated Hodgkin patients. The latter is referred to as subacute motor neuronopathy to emphasize the presumed anterior horn cell localization. Motor deficits predominate in most cases. In the lower extremity, where bilateral exposure to nerve elements is the norm, the deficits are typically bilateral and asymmetric. Monomelic presentations do occur.

DIFFERENTIAL DIAGNOSIS The differential diagnosis of the motor neuron diseases includes disorders in which weakness occurs in the absence of significant pain and/or sensory symptoms. This includes other motor neuron diseases including ALS, myopathies, disorders of neuromuscular transmission and occasional peripheral neuropathies in which motor signs dominate. Differential diagnostic considerations vary with each of the disorders described above and depend in large part on age of onset, speed of progression, and pattern of weakness. The differential diagnosis of infantile SMA I is that of the floppy infant. The majority of these hypotonic neonates will be afflicted with a central nervous system disorder. An alert and appropriately interactive child with diminished or absent deep tendon reflexes would increase the probability of a neuromuscular cause of hypotonia. Within this category, neonatal or congenital myasthenia, neonatal myotonic dystrophy, Pompe disease, nemaline, myotubular or other congenital myopathies, infantile botulism, and rare hypomyelinating neuropathies are the major considerations. SMA II, III, and IV need to be differentiated from a wide variety of myopathic disorders, including the dystrophinopathies, limb-girdle, myotonic and Emery-Dreifuss muscular dystrophies, dermatomyositis, the congenital myopathies, mitochondrial disorders, and lipid and glycogen storage disorders. Chronic inflammatory demyelinating polyradiculoneuropathy would be the primary neuropathic consideration. Kennedy disease may be misdiagnosed as ALS. The Lambert– Eaton myasthenic syndrome, myasthenia gravis, and myopathy with a similar potential pattern of weakness are other diagnostic possibilities. In view of its propensity to affect older individuals and cause symptomatic dysphagia as well as limb weakness, inclusion body myositis and oculopharyngeal muscular dystrophy are the principal myopathic considerations. Focal limb onset presentations of motor neuron disease are commonly mistaken as mononeuropathies, radiculopathies, or plexopathies. The absence of pain and sensory symptoms should deflect consideration away from these disorders. The age of onset, the speed of disease progression, and the presence or



CHAPTER 68  •  Other Motor Neuron Diseases and Motor Neuropathies  649

absence of “bulbar” dysfunction and UMN signs would all aid in the determination of whether ALS, MMN, Hirayama disease, Davidenkow disease, or inclusion body myositis represent the leading consideration. The distal SMAs are frequently misdiagnosed as the more common CMT disease. Polio and other “anterior horn cell tropic” viruses enter into the differential diagnosis of other causes of acute generalized weakness in which weakness predominates over sensory symptoms. The Guillain–Barré syndrome, botulism, hypokalemia, and hypophosphatemia and a number of toxic neuropathies are chief considerations in this regard. The differential diagnosis of HSP includes other causes of spastic paraparesis. Compressive myelopathies, inflammatory, immune-mediated myelopathies such as multiple sclerosis, and neuromyelitis optica deserve consideration. Primary lateral sclerosis (PLS) may provide a source of confusion as it is usually a slowly progressive upper motor neuron disorder. PLS commonly produces functional impairments of the upper extremities and of bulbar function unlike HSP. PLS would not typically include cavus foot deformities or large fiber sensory loss in the feet. Vitamin B12 and copper deficiency should be considered as potentially treatable causes of spastic paraparesis. In both cases, these disorders are typically more rapid in their onset as well as dominated by signs of posterior column involvement. The corticospinal tracts may be affected by retroviral infection, and both the HIV and HTLV1 viruses need to be considered in the appropriate clinical context. Other hereditary neuro­degenerative disorders that affect the corticospinal tracts, the leukodystrophies, particularly adrenoleukodystrophy in young adult women, and the spinocerebellar atrophies are considerations.

DIAGNOSTIC APPROACH The diagnostic approach is dependent on the index of clinical suspicion for a given disorder, and the availability and affordability of genetic testing. Of the disorders discussed in this chapter, mutational analysis is currently commercially available for SMA types I–IV, Kennedy disease, and a few of the dominantly inherited forms of HSP. As the cost of this testing is currently substantial, it would be reasonable to utilize these tests only when a high degree of clinical suspicion exists and not as a screening tool. The majority of tests are performed with a goal of excluding other diagnostic considerations. Electrodiagnostic testing (EDX), that is, EMG and nerve conduction testing, has the greatest utility in this regard and often serves to support if not define an MND diagnosis. The characteristic pattern in the majority of MNDs is normal sensory nerve conductions, low amplitude or absent compound muscle action potentials in affected limbs, and normal or mildly reduced conduction velocities. The needle exam demonstrates reduced recruitment of motor unit action potential (MUAPs) that are long duration and high amplitude in their morphology, indicative of chronic partial denervation and reinnervation; ongoing denervation in the form of fibrillation potentials and positive waves is also seen. Rarely, one can see fasciculation potentials.

Electromyography

Nerve Conduction Velocity Response of hypothenar muscles to ulnar nerve stimulation Response Response (Normal conduction velocity) to stimulus to stimulus at wrist at elbow F wave normal

Stimulus

0

3

8

Response to stimulus at wrist

Milliseconds Response to stimulus at elbow

0

3

8

Response to stimulus at wrist

F wave delayed

Milliseconds

Response to stimulus at wrist Stimulus

0

6

Voluntary activity

Response to stimulus at elbow

17

At rest Slight dropout of motor units

38

Voluntary activity

(Slow conduction velocity) Dispersed CMAP

6

Normal number of motor units

(Normal conduction velocity)

Stimulus

0

At rest

25

Normal CMAP

Stimulus

Voluntary activity

At rest No F wave Greater dropout of motor units

Milliseconds

No response (Conduction velocity to stimulus not calculable) at elbow Dispersed low-amplitude No F wave CMAP Milliseconds

Voluntary activity At rest Fibrillations

Rare single motor unit firing

Figure 68-6  Multifocal Motor Neuropathy: Conduction Block on Nerve Conduction Study.

For the most part, the only EDX features that distinguish between the different motor neuron diseases are the distribution of abnormalities and the degree of active versus chronic denervation changes. More chronic disorders such as Kennedy disease or old polio are dominated by features of chronic denervation and reinnervation whereas ALS typically has prominent features of both active and chronic denervation. Kennedy disease is rather unique within the MND spectrum in that sensory nerve action potential amplitudes are often reduced or absent. A key diagnostic feature in MMN is the presence of demyelinating features on motor nerve conductions, particularly the presence of conduction block (Fig. 68-6). Unfortunately, there are a number of reasons why this feature is not always demonstrable. Creatine kinase is often modestly elevated in many of the MNDs, to levels of 200–500 U/L and occasionally to levels greater than 1000 U/L. Antibodies directed against the GM1 ganglioside are found in high titer in the serum of 30–80% of patients with MMN but are neither sensitive nor specific. MR imaging of proximal nerve may identify focal areas of increased signal that are supportive of an MMN diagnosis. Lumbar puncture is of value if an infectious cause of motor neuron disease is suspected but otherwise has limited value. Testing in HSP is done primarily to identify or exclude other disorders that may produce a spastic paraparesis. Somatosensory evoked potentials may serve to confirm involvement of the posterior columns and exclude consideration of primary lateral sclerosis. Prior to the availability of genetic testing, muscle biopsies were routinely performed in Werdnig–Hoffman suspects. A

650  SECTION XVI  •  Motor Neuron Disorders

characteristic but nondiagnostic pattern consists of sheets of small rounded atrophic fibers with small islands of hypertrophied type 1 muscle fibers. Muscle biopsy in any MND will demonstrate some pattern of neurogenic atrophy that may include angulated atrophic fibers, target fibers, pyknotic nuclear clumps, and particularly muscle fiber type grouping and grouped atrophy. Usually there is no role for nerve biopsy in any of the disorders discussed in this chapter.

MANAGEMENT AND THERAPY Unfortunately, management in the majority of these disorders remains symptomatic and supportive, with the primary goals of education, maintenance of safety, and independent function. With the exception of MMN, specific and effective treatments do not currently exist for these disorders. Knowledge of the defective gene product in SMA I–IV has led to rational therapeutic trials. Ventilatory failure in SMA I and II is inevitable; tracheostomy and long-term mechanical ventilation, and insertion of a percutaneous feeding tube are decisions with enormous emotional consequences to the parents of an affected child. Noninvasive positive pressure ventilation may provide an improved quality and duration of life until a decision regarding tracheostomy is required. Results of clinical trials utilizing gabapentin, riluzole, acetylcarnitine and phenylbutyrate on patients affected with SMA I–III are negative, inconclusive, or incomplete to date. Valproic acid can increase the rate of SMN2 transcription. Recently, an observational study demonstrated that valproate appeared to increase strength by a mean of 16% in SMA type III and IV patients. Valproate therapy is not without risk, including liver toxicity and carnitine deficiency. Its use in SMA patients outside of a clinical trial is not recommended. The development of kyphoscoliosis is a common problem in children with SMA who are wheelchair bound. Spine stabilization is commonly recommended in individuals whose curves exceed 50 degrees and whose vital capacities exceed 40% of predicted. The goals of this intervention are patient comfort and potential stabilization of restrictive pulmonary deficits. A high index of suspicion is maintained for symptoms of impaired nocturnal ventilation and if necessary treated with application of positive airway pressure. With Hirayama disease, decompression of the cervical spinal cord has been attempted. It is unclear whether this meaningfully affects the natural history of the disease. Treatment for HSP is supportive. There are a number of different options to reduce spasticity, including oral tizanidine, baclofen, dantrolene, benzodiazepines, intrathecal baclofen, or botulinum toxin injections directly into spastic muscles. The goal of treatment is to improve mobility, augment range of motion, and relieve the discomfort associated with spastic muscles. In an individual who also has considerable underlying weakness, the increased tone of extensor muscles may represent the major source of antigravity resistance. Suppression of this tone may deprive an individual of his or her ability to stand. Home modification and durable medical equipment are important components of the management of patients with chronic neuromuscular diseases. The goals are to maintain

independent mobility and patient safety simultaneously. Ankle– foot orthoses are of great benefit to individual patients. Their primary purpose is to prevent tripping by maintaining the foot in a partially dorsiflexed position. A skilled physical therapist is invaluable to decide whether a cane, Lofstran crutches, a walker or a wheelchair is the best solution for an individual patient. Motorized scooters or power wheelchairs are options for patients who lack the ability to propel a manual chair but who have enough upper extremity function to operate either of these. Although scooters are more attractive to patients, they are often disadvantageous as they require a greater degree of upper extremity function to operate, provide less trunk support, and allow for less additional equipment to be mounted on them. In patients who live in multiple-story dwellings, stair lifts provide a safe option. A skilled occupational therapist is also a valuable aid in maintaining independence in activities of daily living.

FUTURE DIRECTIONS As most of these disorders are heritable, effective treatment may depend on future technological advances that might allow for the identification and restitution of the affected genes in utero. Truncating the effects of mutated genes pharmacologically and arresting disease progression appears to be another interventional strategy that may be feasible in the near future at least in certain diseases. Reversing the established consequences of these mutations will be a more daunting challenge. ADDITIONAL RESOURCES SMA http://www.mda.org/disease/ www.nlm.nih.gov/medlineplus/spinalmuscularatrophy.html http://www.ncbi.nlm.nih.gov/sites/entrez?db=omim HSP Spastic Paraplegia Foundation, Inc. 209 Park Rd. Chelmsford MA 01824 Phone: 703-495-9261 [email protected] sp-foundation.org National Ataxia Foundation 2600 Fernbrook Lane Suite 119 Minneapolis MN 55447 Phone: 763-553-0020 Fax: 763-553-0167 [email protected] Bertini E, Burghes A, Bushby K, et al. 134th ENMC International Workshop: Outcome measures and treatment of spinal muscular atrophy 11-13 February 2005. Naarden, The Netherlands. Neuromuscular Disorders 2005;15:802-816. Chahin N, Klein C, Mandrekar J, et al. Natural history of spinal-bulbar muscular atrophy. Neurology 2008;70;1967-1971. Harding, AE. Inherited neuronal atrophy and degeneration predominantly of lower motor neurons. In: Dyck PJ, Thomas PK, Griffin JW, Low PA, Poduslo JF, editors. 3rd ed. Peripheral Neuropathy. Philadelphia: W. B. Saunders; 1993. p. 1051-1064. Irobi J, Dierick I, Jordanova A, et al. Unraveling the genetics of distal hereditary motor neuropathies. Neuromolec Med 2006;8:131-146.

Stiff Person Syndrome Ted M. Burns, Juliana Lockman, and H. Royden Jones, Jr.

T

his chapter concentrates on the most common of the very uncommon motor neuron hyperactivity disorders, namely the stiff person syndrome. Two other potentially related syndromes characterized by incomplete relaxation or inhibition of motor neurons—Isaac (Merten) syndrome and neuromyotonia —are discussed in Chapter 70.

Clinical Vignette A 53-year-old woman with myeloid metaplasia reported a 6-month history of severe back pain, difficulty walking, and occasional falls. No lumbosacral disc disorder could be identified. During the past month, these spasmodic muscle pains of her legs, back, and abdomen were induced by attempting to sit up, stand, or walk. Occasionally, these spasms led to stiffening of her entire body; at their extreme these induced urinary incontinence. At times, the severity of the pain led her to cry out to such a degree that it caused one observer to liken her distress to that of a “bellowing cow”! These outbursts led to her being referred to a psychiatrist. Neurologic examination demonstrated an anxious and alert middle-aged woman. The primary finding was her spontaneous reaction to the slightest sensory stimuli wherein she totally stiffened, reminding this neurologist (HRJ) of a tetanus patient. Other than hyperlordosis, marked hyperreflexia at her knees and a right Babinski sign, her basic neurologic examination was normal. However, on a neurosurgeon’s brusque attempt to get her out of bed to stand, she developed severe painful body spasm and fell into the hospital room wall as if a chain saw had cut her legs off. Head and cervicothoracic spine magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) study were normal, as was serum B12 level. Nerve conduction studies were normal. Her needle electromyography (EMG) study demonstrated prolonged motor unit activity in contracting muscles during episodes of stiffness and spasm but was otherwise normal. Double-antibody radioimmunoassay demonstrated a high level of serum glutamic acid decarboxylase 65 (GAD-65) antibodies (138 nmol/L; reference range: ≤0.02 nmol/L). The patient was diagnosed with stiff person syndrome (SPS). Increasing doses of diazepam alleviated symptoms at a dose of 60 mg daily. A course of plasmapheresis treatments followed by prednisone (80 mg daily) led to gradual symptomatic improvement. She was successfully tapered off corticosteroids during a 2-year period and diazepam over 5 years.

The stiff person syndrome (SPS, originally known as the stiff man syndrome) was first described by Moersch and Woltman in 1956. Classic stiff person syndrome is a chronic autoimmune

69 

disease characterized by spine and leg rigidity with lumbar hyperlordosis and painful spasms. Women are more often affected than men at a ratio of 2 : 1. This disorder generally presents in the fourth through sixth decades. Its onset is typically insidious and the course is usually progressive. Laboratory studies that are classically abnormal in SPS include an elevated serum GAD-65 antibody titers (>20 nmol/L), needle EMG findings of continuous motor unit activity in at least one axial muscle, and normal brain MRI and CSF studies. Variants of SPS include those with focal limb dysfunction (stiff limb syndrome), encephalomyelitis (“SPS Plus”), and those associated with paraneoplastic antibodies, namely, amphiphysin as seen with breast cancer. Although most instances of SPS do not have a family history, at least one instance of such is reported. Interestingly the parent and propositus had a stiff limb variant and the daughter a purely intermittent axial presentation initially diagnosed as hysteria or anxiety disorder because of her presentation with recurrent opisthotonus.

ETIOLOGY The findings that support an autoimmune basis for SPS are the following: (1) SPS is associated with autoantibodies, both the classic GAD-65 antibodies and a paraneoplastic variant, amphiphysin antibodies; (2) SPS is frequently accompanied by other autoimmune disorders such as type 1 diabetes, thyroiditis, vitiligo, and pernicious anemia; and (3) intravenous immunoglobulin (IVIg) and plasma exchange provide effective treatments for some patients. The precise pathophysiologic role for the specific antibodies is unclear, although it is speculated that the autoimmune lesions are directed at a site on the inhibitory spinal interneurons (Fig. 69-1). Although a direct relation is inferred, this is not fully substantiated. Factors supporting a direct role for antibodies are (1) the finding of elevated intrathecal GAD antibodies; (2) the antibody concentration correlates with the degree of motor excitability; (3) GAD antibodies, obtained from serum of stiff person patients, inhibit both GAD and GABA synthesis in vitro.

CLINICAL PRESENTATION Classic SPS Typically this is characterized by spine and leg rigidity with lumbar hyperlordosis as a key feature (Figs. 69-2 and 69-3). Lower extremity rigidity can cause full extension of the legs, making walking difficult. Patients often also experience superimposed painful spasms that may be precipitated by sudden noise, anxiety, or touch. The spasms can be of such abrupt onset and power that these individuals may unexpectedly and precipitously fall. Patients soon recognize that emotional stress often provokes their spasms. They may develop agoraphobia secondary to the fear of falling in public. Neurologic examination



CHAPTER 69  •  Stiff Person Syndrome  653

Excites phasic flexors Renshaw cell To flexors Inhibits tonic extensors

To extensors

Figure 69-1  Renshaw Cell Bias.

sometimes reveals paraspinal and abdominal musculature contraction with lumbar hyperlordosis and lower limb rigidity. However, these findings are often not present until late in the clinical course. The muscle stretch reflexes may be normal to brisk, with occasionally extensor plantar responses.

Stiff Person Syndrome—Primary Limb Involvement This variant of stiff person syndrome presents focally with rigidity and spasms involving one or more limbs. In “stiff limb syndrome,” motor symptoms predominantly affect the limb distally. In contrast to the more traditional SPS, axial involvement is less prominent. However, significant proximal muscle involvement does eventually occur if the SPS is not diagnosed and treated early. This was illustrated by one of our patients who had spontaneous quadriceps spasms leading to automobile accidents. These were spontaneous and precipitous contractions leading him to suddenly apply excess pressure to the accelerator on one occasion and the brake on another. GAD autoantibody titers are elevated less frequently in these patients. The EMG pattern is even less predictable in these more limited forms.

Occasional patient with stiff person syndrome assumes hyperextended posture with increased lordosis. Figure 69-2  Stiff Person Syndrome.

Stiff Person Syndrome with Encephalomyelitis (SPSE) Patients with stiff person syndrome with encephalomyelitis typically present with a subacute onset of axial or limb rigidity accompanied by pyramidal tract signs (e.g., abnormally brisk muscle stretch reflexes, Babinski sign), brainstem dysfunction, cognitive decline, and myoclonus. The variant syndrome is often paraneoplastic, and amphiphysin antibodies are frequently present. Paraneoplastic stiff person syndrome is associated with several malignancies, including breast adenocarcinoma, small cell lung cancer, colon cancer, and Hodgkin lymphoma. It is not unusual for the SPS to be the first sign of the underlying malignancy. Thus, when amphiphysin antibodies are positive, it is important to ensure careful follow-up. One patient had two negative mammograms over a 1-year period only to self-discover a breast mass a short time later.

Patient rigid in moderate opisthotonos, with arms extended and boardlike abdomen mimicking tetanus. Figure 69-3  End-Stage Stiff Person Syndrome.

654  SECTION XVII  •  Neuromuscular Hyperactivity Disorders

DIFFERENTIAL DIAGNOSIS Frequently SPS patients have a history of a number of nondiagnostic visits to a variety of physicians, including a few neurologists. They are often inappropriately labeled as hysteric or having a functional somatoform disorder leading to recurrent psychiatric evaluations. Other erroneous diagnoses sometimes applied to these patients include chronic tetany, tetanus, dystonia, stroke, and arthritis. The possibility of a spinal cord disorder (i.e., a myelopathy with spondylosis or disc herniation), or a basal ganglia disorder also requires consideration. In any acute setting, the possibility of tetanus must be considered because of the board-like stiffening of the abdomen and the severity of muscle spasms. Sparing of the jaw muscles and absence of trismus in SPS makes tetanus unlikely. Spasms are generally less violent and of less acute onset in SPS than in tetanus, but this is not invariable. Chronic tetanus is rare and typically presents with trismus and risus sardonicus. Hereditary hyperekplexia or startle disease with startleinduced spasms is a rare disorder caused by mutations in the glycine receptor, a receptor for a major inhibitory central nervous system (CNS) neurotransmitter. Startle-induced spasms may also be seen in focal spinal cord lesions such as tumors or syringomyelia. Patients with psychogenic muscle contraction or spasm usually have a consistently inconsistent as well as more variable presentation; this diagnosis must only be entertained after long periods of careful observation and recurrent laboratory testing. Such cases occur occasionally but warrant consideration. Other causes of muscular rigidity include disorders of muscle or neuronal membrane hyperexcitability. Two channelopathies with muscle rigidity, namely myotonia congenita and Isaac syndrome, deserve consideration in the differential diagnosis, but neither of these is associated with the pain typically seen with SPS. Multiple sclerosis, poliomyelitis, Lyme disease, spinal myoclonus, tumors, and even strychnine poisoning are also in the differential and might deserve consideration in some cases.

DIAGNOSTIC APPROACH Stiff person syndrome is primarily a clinical diagnosis, and diagnostic criteria include: 1) Stiffness and rigidity initially affecting axial muscles or occasionally an individual limb. 2) Progressive involvement affecting proximal limb muscles. 3) Abnormal axial posture with increased lumbar hyperlordosis. 4) Superimposed muscle spasms. 5) No brainstem, extrapyramidal, or lower motor neuron signs. 6) No sphincter and sensory disturbance, and no cognitive involvement. 7) Clinical response to diazepam or another benzodia­ zepine. 8) Markedly elevated GAD-65 autoantibody titers in serum support the diagnosis; 60–90% of classic SPS patients

have very high titers of GAD-65 in serum, usually greater than 20 nmol/L. Significantly lower levels of GAD-65 antibodies are frequently seen in type 1 diabetes mellitus, drug-resistant epilepsy, cerebellar degeneration syndromes, and Batten disease. 9) Early on in this disorder EMG is often normal. However, EMG eventually reveals a characteristic abnormality with concomitant and continuous firing of motor unit potentials in both agonist and antagonist muscles in severely affected individuals. The lack thereof of characteristic EMG findings should not be a reason to dismiss the diagnosis. Other studies will prove to be very important to exclude competing differential diagnostic considerations. Magnetic resonance imaging of the brain and spinal cord is normal but can be useful in identifying mimics of the variant with encephalomyelitis (see below). The cerebrospinal fluid is usually normal but can occasionally demonstrate increased CSF protein, oligoclonal bands, or IgG. It must be emphasized that if one waits until all of the above classic “requisites” for diagnosis of SPS are fulfilled, the opportunity for significant therapeutic control of the potentially future downhill course of this eventually lethal disorder will be missed. This is illustrated by some of the early variants as noted below.

TREATMENT AND PROGNOSIS Symptomatic Treatment These medications may be very helpful but do not address the basic autoimmune process in this chronic disorder. BENZODIAZEPINES

Diazepam is the first-line symptomatic therapy. It was the first pharmacologic agent shown to dramatically alter the clinical course of SPS. Its use is associated with significant clinical improvement in stiffness, frequency of spasms, and ability to ambulate. Benzodiazepines are GABAA receptor agonists and thus can act to inhibit the excessive MUP firing leading to the painful muscle contraction of SPS. Common side effects include sedation, somnolence, fatigue, and ataxia. Serious side effects include hypotension, respiratory depression, and long-term physical dependence. Much caution is advised if one considers discontinuation of a benzodiazepine. This should involve a carefully monitored and very slow taper with the avoidance of an abrupt withdrawal as it can be lethal, possibly secondary to arrhythmias. BACLOFEN

Baclofen is also considered a first-line therapy. Baclofen is a GABAB receptor agonist that also can inhibit the excessive muscle contraction of SPS. Common side effects include constipation, nausea, decreased muscle tone, headache, dizziness, and somnolence. Seizures and even death secondary may occur with abrupt withdrawal of baclofen.



Immunosuppressants/Immunomodulators CORTICOSTEROIDS

Corticosteroids are the first-line immunosuppressive therapy requiring a high dose (e.g., prednisone 1 mg/kg/d). Once patients become asymptomatic, they usually require long-term maintenance therapy, followed by a gradual taper as tolerated. The usual side affects need to be monitored. INTRAVENOUS IMMUNOGLOBULIN

Intravenous immunoglobulin (IVIg) is another consideration for SPS patients refractory to symptomatic management with first-line agents. IVIg is generally well tolerated; its biggest downside is cost and availability. Corticosteroids, in contrast, are very inexpensive but generally cause more side effects. It is not clear whether long-term treatment with one modality per se is better than the other. PLASMA EXCHANGE

Plasma exchange has demonstrated mixed clinical efficacy. It is sometimes considered in combination with first-line agents as a short-term management option. AZATHIOPRINE

Azathioprine is a reasonable long-term option for patients who fail conventional regimens, but clinical improvement is often delayed 4–6 months after initiation of therapy. RITUXIMAB

Rituximab, an anti-CD-20 monoclonal antibody that attacks B lymphocytes, has been reported to lead to clinical improvement

CHAPTER 69  •  Stiff Person Syndrome  655

of SPS. GAD-65 antibodies become undetectable and the EMG normalizes within weeks. However, more studies of Rituximab in SPS need to be performed before it becomes a first-line immunosuppressive choice.

Other Issues Psychiatric problems commonly accompanying SPS include anxiety, depression, and substance abuse. These may exacerbate both the chronic stiffness and the frequency of spasms. Psychiatric consultation can play an important role in the identification and treatment of such problems. ADDITIONAL RESOURCES Amato AA, Cornman EW, Kissel JT. Treatment of stiff-man syndrome with intravenous immunoglobulin. Neurology 2004;44:1652-1654. Barker RA, Revesz T, Thom M, et al. Review of 23 patients affected by the stiff person syndrome: clinical subdivision into stiff trunk (man) syndrome, stiff limb syndrome, and progressive encephalomyelitis with rigidity. J Neurol Neurosurg Psychiatry 1998;65:633-640. Burns TM, Jones Jr HR, Phillips II LH, et al. Two generations of clinically disparate stiff man syndrome, confirmed by significant elevations of GAD65 autoantibodies. Neurology 2003;61:1291-1294. Dalakas MC, Li M, Fujii M, et al. Stiff person syndrome: quantification, specificity, and intrathecal synthesis of GAD 65 antibodies. Neurology 2001;57:780-784. Lockman J, Burns TM. Stiff-person syndrome. Current Treatment Options Neurol 2007;9:234-240. Moersch FP, Woltman HW. Progressive fluctuating muscular rigidity and spasm (“stiff-man” syndrome): report of a case and some observations in 13 other cases. Mayo Clin Proc 1956;31:421-427. The initial and very classic paper with exquisitely detailed patient history

Other Peripheral Motor Hyperactivity Syndromes H. Royden Jones, Jr.

ISAAC (MERTEN) SYNDROME/QUANTAL SQUANDER, NEUROMYOTONIA This is another hyperkinetic presumed peripheral nerve hyperexcitability syndrome that occurs even more rarely than the stiff person syndrome. As noted above, there are a number of synonyms. It is a very unusual neurologic disorder also characterized by the continuous firing of peripheral nerves, and thus muscle fibers. It is much more subtle in its presentation. Typically the age of onset is in the teenage years, but it may be seen in adulthood. This appears to be autoimmune in origin (anti– potassium channel antibodies are positive in some patients.) This is a nonspecific finding per se as these antibodies may be found in a variety of neurologic syndromes. Here the patient first notes what appears to be an almost continuous firing of groups of muscle fibers usually appearing to mimic fasciculations. These occur concomitantly in both agonists and antagonists. The patient often notes a sense of fatigue. Usually there are no significant associated muscle spasms, cramping, or pain; however, in some instances such may occur. The patient may note a degree of weakness because of the inconsistent firing of opposing muscle groups, leading to ineffective mechanical function. Some patients have excessive sweating. Other than the apparent pseudo-fasciculations and a hint of muscle weakness, the neurologic examination is normal. Diagnosis is suggested when electromyography (EMG) demonstrates continuous firing of normal motor unit potentials without any abnormalities on insertion. These persist even during sleep. A therapeutic trial of phenytoin or carbamazepine most always leads to a complete cessation of all aspects of this syndrome. This therapeutic result serves to confirm the suspected diagnosis. This is a particularly gratifying diagnosis to make as some of these extremely unusual patients may have received an earlier clinical diagnosis of amyotrophic lateral sclerosis (ALS).

CRAMP FASCICULATION SYNDROME This is a rare peripheral nerve hyperexcitability syndrome that has similarities to Isaac syndrome, but with the added feature of pain and cramps. When EMG is performed, motor nerve stimulation results in a sustained contraction of the activated muscle. Some but not all of these patients may have potassium channel antibodies. Treatment is similar to that for Isaac syndrome.

BENIGN FASCICULATION SYNDROME These patients seemingly develop the relatively rapid onset of scattered fasciculations that occur much less frequently than

70 

those seen in Isaac syndrome. This is obvious by both clinical examination and EMG. The major issue here is the patient who is medically knowledgeable and makes an association between fasciculations and ALS. However, if there is no concomitant clinical weakness and/or muscle atrophy, this almost always is a benign idiopathic entity. Its importance lies in the need for the neurologist to respond immediately to the concern of their medical colleague by performing a very careful clinical evaluation followed by an EMG. If both areas are normal, the patients can be told that they have no greater risk to have ALS than any other healthy individual. Often such physicians and nurses have waited to seek expert attention for a matter of months while trying to ignore their symptoms. Finally they become so overwhelmed that they seek help often calling to say that they do have ALS. We look upon this request as a neurologic social emergency in order to immediately allay the angst of our colleagues. The emotional relief that is expressed by these colleagues when they hear the good news is heart warming.

MYOKYMIA This very uncommon finding is a subcutaneous vermification, or worm-like activity, of just a few muscles. These patients often rarely note these muscle twitches. They are very rhythmic and are basically a quivering under the skin. Typically these are seen in two neurologic conditions. The most common setting is the patient with prior breast cancer who had a mastectomy many years earlier that was followed soon after surgery by radiation. After a many-year postradiation delay, sometimes as much as 20+ years, the patient begins to note weakness and atrophy in the adjacent arm and hand muscles. With careful inspection one may rarely note the myokymia. However, EMG will demonstrate the spontaneous rhythmic firing of grouped motor unit potentials. These are so unique that they provide strong evidence that the patient’s plexopathy is a consequence of radiation. Subtle peripheral facial nerve lesions associated with a contiguous pontine glioma may also be characterized by myokymia. Here the subcutaneous tissue is so thin that the myokymia is clinically evident to the patient. They may note these adventitious movements when shaving or applying lipstick. In this instance, a magnetic resonance imaging is indicated to search for a pontine mass. On rare occasions, myokymia occurs subsequent to Bell palsy or spontaneously without a specific pathologic lesion. ADDITIONAL RESOURCES Benerud MD, Windebank A, Daube J. Long term follow-up of 121 patients with benign fasciculations. Neurology 1993;34:622. Newsom-Davis J. Neuromyotonia. Rev Neurol 2004;160:85.

Hereditary Polyneuropathies Monique M. Ryan

Clinical Vignette A 15-year-old boy presents with frequent tripping and exercise intolerance. He falls frequently and tires easily. He was born at term after an uncomplicated pregnancy. His early developmental milestones were normal until he walked late, at 20 months of age. On examination, he has mild wasting of the distal lower extremities without contractures. He walks well on his toes but cannot walk on his heels. There is mild weakness of ankle dorsiflexion and eversion. The ankle jerks are absent even with reinforcement, but other reflexes are preserved. Sensation is intact. There is no family history of neuromuscular disorders, but on examination his father has high-arched feet with distal weakness and generalized areflexia. Neurophysiologic testing of the patient and his father reveals marked slowing of motor nerve conduction, of the order of 18 m/s, with absent sensory responses. Genetic testing is positive for a duplication of the PMP22 gene on chromosome 17, confirming the clinical diagnosis of Charcot–Marie–Tooth disease type 1A.

T

he hereditary motor and sensory neuropathies (HMSNs) account for approximately 40% of chronic neuropathies. There are now more than 40 known genes or loci for the various forms of HMSN, which are collectively known as Charcot– Marie–Tooth disease (CMT). About 1 in 2500 persons is affected by CMT. New genes or loci for CMT subtypes are identified very frequently. Less common inherited polyneuropathies are those associated with systemic genetic disorders and inborn errors of metabolism (Table 71-1). Advances in genetic characterization of the inherited neuropathies have afforded greater insight into their biologic basis, and there is increasing interest in therapeutic strategies for these disorders, which can cause lifelong morbidity related to weakness, sensory loss, and orthopedic complications.

ETIOLOGY AND PATHOGENESIS Charcot–Marie–Tooth disease is commonly divided—on the basis of inheritance, neurophysiologic findings, and histopathology—into demyelinating forms (including dominantly inherited subtypes, CMT1 and CMT3, and autosomal recessive forms, CMT4) and axonal neuropathies (CMT2, which can have either dominant or recessive inheritance). Other forms of CMT include hereditary sensory and autonomic neuropathy (HSAN), which has prominent sensory and autonomic features, and distal hereditary motor neuropathy (dHMN), which has pure motor findings with no clinical or neurophysiologic evidence of sensory deficits. Regardless of their genetic basis, the final common pathway of all neurologic deficits in the inherited neuropathies is lengthdependent axonal degeneration, which accounts for the clinical

71 

findings common to many forms of CMT. Neurophysiologic studies variably demonstrate changes of demyelination, axon loss, or a combination of these findings.

CLINICAL PRESENTATION CMT generally first manifests in the first decade but progresses slowly, presenting in childhood or early adulthood with an abnormal gait or pes cavus. Less commonly, CMT presents in infancy with hypotonia and delayed motor milestones, or in late adulthood. The cardinal features of the genetic polyneuropathies are distal muscle wasting and weakness, loss of the deep tendon reflexes, and impaired distal sensation. The gait is highstepping because of foot drop. Nerve hypertrophy may be palpable in the neck or at the elbow (Fig. 71-1) or nerve enlargement may be seen on magnetic resonance imaging (MRI) (Fig. 71-2). Orthopedic deformities develop in at least two thirds of CMT patients. The most common finding is pes cavus, caused by imbalance between the muscles of the posterior and anterior compartments of the leg. With time, foot deformities become fixed and can cause pain, pressure areas, and stress fractures. Scoliosis and developmental hip dysplasia are less common complications of CMT. The clinical evaluation should include inquiry as to the family history. Consanguinity suggests a possible recessive inheritance, whereas male-to-male transmission excludes an X-linked condition.

DIFFERENTIAL DIAGNOSIS A hereditary neuropathy is suggested by a long, slowly progressive course, clinical findings such as pes cavus (which suggests long-standing weakness), and relatively prominent motor deficits without positive sensory phenomena. Acquired neuropathies have a shorter time course, are more likely to be associated with painful sensory phenomena, and may be associated with systemic symptoms or signs.

DIAGNOSTIC APPROACH Careful clinical evaluation is very important. Often no family history can be obtained, either because a case is sporadic, or because less severely affected relatives have not been diagnosed. Clinical examination and targeted neurophysiologic and genetic testing may reveal relatives to be also affected by hereditary neuropathies. In patients with suspected neuropathies, the initial investigation will generally be nerve conduction studies and electromyography (Fig. 71-3). CMT is classified as demyelinating if the median nerve motor conduction velocity (MCV) is less than 38 m/s, or axonal (CMT2) if the median MCV is more than 38 m/s. Axonal (neuronal) neuropathies are also associated with low-amplitude sensory and motor responses. Intermediate



CHAPTER 71  •  Hereditary Polyneuropathies  659

Table 71-1  Classification of Inherited Polyneuropathies Inheritance

Neurophysiology Demyelinating Axonal

Hereditary sensory and autonomic neuropathies Hereditary motor neuropathies Hereditary neuropathy with liability to pressure palsies

Autosomal dominant Autosomal dominant Autosomal recessive Autosomal/de novo dominant Autosomal recessive Autosomal dominant X-linked dominant, X-linked recessive Autosomal recessive Autosomal dominant Autosomal dominant

Other Inherited Neuropathies Hereditary neuralgic amyotrophy Familial amyloid polyneuropathy Giant axonal neuropathy Infantile neuroaxonal dystrophy Andermann syndrome

Autosomal Autosomal Autosomal Autosomal Autosomal

Axonal Axonal Axonal Axonal Axonal

Hereditary motor and sensory neuropathy type 1 Hereditary motor and sensory neuropathy type 2 Hereditary motor and sensory neuropathy type 3 Hereditary motor and sensory neuropathy type 4 Intermediate CMT X-linked CMT

Neuropathies Associated with Inborn Errors of Metabolism Lipid Disorders Cerebrotendinous xanthomatosis Abetalipoproteinemia, hypolipoproteinemia Ataxia with vitamin E deficiency Peroxisomal Disorders Refsum disease Adrenomyeloneuropathy Mitochondrial Cytopathies NARP MNGIE Leigh disease Lysosomal Enzyme Diseases Globoid cell leukodystrophy Metachromatic leukodystrophy Fabry disease Tyrosinemia type 1 Sphingomyelin Lipidoses Niemann–Pick disease type C Farber disease Porphyrias Acute intermittent porphyria Hereditary coproporphyria Variegate porphyria

dominant dominant recessive recessive recessive

Demyelinating Demyelinating Mixed Mixed Axonal Axonal Demyelinating

Autosomal recessive Autosomal recessive Autosomal recessive

Mixed Demyelinating Demyelinating

Autosomal recessive X-linked

Demyelinating Axonal

Autosomal recessive Autosomal recessive Autosomal recessive

Mixed Mixed Mixed

Autosomal recessive Autosomal recessive X-linked Autosomal recessive

Demyelinating Demyelinating Axonal Axonal

Autosomal recessive Autosomal recessive

Demyelinating Demyelinating

Autosomal dominant Autosomal dominant Autosomal dominant

Axonal Axonal Axonal

Disorders with Defective DNA Synthesis or Repair Ataxia telangiectasia Cockayne syndrome

Autosomal recessive Autosomal recessive

Axonal Demyelinating

Neuropathies Associated with Spinocerebellar Ataxias Friedreich ataxia, other SCAs Neuroacanthocytosis

Autosomal recessive Autosomal recessive

Axonal Axonal

MNGIE, mitochondrial neurogastrointestinal encephalopathy; NARP, neuropathy, ataxia, and retinitis pigmentosa; SCA, spinocerebellar ataxia.

forms of CMT have median MCVs in the 25–45 m/s range. In the hereditary demyelinating neuropathies, neurophysiologic abnormalities are generally homogeneous, with uniform slowing of motor and sensory nerve conduction. In contrast, the acquired demyelinating neuropathies (such as Guillain–Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy) are characterized by patchy involvement of peripheral nerves with focal slowing, conduction block, and dispersion of motor responses (Fig. 71-4).

CMT can be inherited in an autosomal dominant, autosomal recessive, or X-linked fashion. Many “sporadic” patients have (new) heterozygous mutations in a gene for an autosomal dominant form of CMT. Others have autosomal recessive CMT. In Western populations, about 90% of cases of CMT are either autosomal dominant or X-linked. Recessive CMT is more frequent in populations in which consanguinity is common. Genetic testing is available for the more common forms of CMT, but for less common phenotypes is often performed only

Swelling of great auricular nerve or other individual nerves, particularly the ulnar or the peroneal nerves; may be visible or palpable Typical genetic chart

Male unaffected

2

Female unaffected Male with CMT 1A disease Female with CMT 1A disease

4

Thin (storklike) legs with very high arch (pes cavus) and claw foot or hammertoes due to atrophy of peroneal, anterior tibial, and long extensor muscles of toes

2

3

3

2

4  wheelchairdependent 3  walks, unable to work

1

3

2  works, with help 1  mild disability, no help required

Figure 71-1  Findings in Charcot–Marie–Tooth Disease.

A and B Coronal T1 and axial proton density with fat-saturated images with normal peroneal and posterior tibial nerves.

Peroneal nerve Posterior tibial nerve

A

B

Posterior tibial nerve Peroneal nerve

C

D

Figure 71-2  MRI Findings in Charcot–Marie–Tooth Disease, with Normal Comparison.

C and D Coronal T1 and axial proton density with fat-saturated images showing enlarged peroneal and posterior tibial nerves in a patient with Charcot-Marie-Tooth disease.



CHAPTER 71  •  Hereditary Polyneuropathies  661

Inherited polyneuropathy

Demyelinating

Intermediate

Axonal

AD PMP22 MPZ LITAF EGR2 NEFL

XL GJB1 PRPS1

AD MFN2 RAB7 MPZ NEFL GARS HSP27 HSP22

AR GDAP1 MTMR2 MTMR13 KIAA1985 NDRG1 EGR2 PRX PMP22 MPZ FGD4 FIG4

AD DMN2 YARS NEFL MPZ AR GDAP1

Electrophysiologic criteria

AR MFN2 GDAP1 LMNA HSP27 KCC3 Gigaxonin IGHMBP2 PLA2

Inheritance pattern

AD, autosomal dominant; AR, autosomal recessive; DMN2, dynamin 2; EGR2, early growth response 2; FGD4, frabin; FIG4, sac domaincontaining inositol phophatase 3; GARS, glycyl-tRNA synthetase; GDAP1, ganglioside-induced differentiation-associated protein 1; GJB1, gap junction protein beta 1; HSP22, heat shock 22 kDa protein 8; HSP27, heat shock 27 kDa protein 1; IGHMBP2, immunoglobulin mu binding protein 2; KIAA1985, K1AA1985 protein; KCC3, potassium-chloride cotransporter 3; LITAF, lipopolysaccharideinduced tumor necrosis factor; LMNA, lamin A/C; MFN2, mitofusin 2; MPZ, myelin protein zero; MTMR2, myotubularin-related protein 2; MTMR13, myotubularin-related protein 13; NDRG1, N-myc downstream-regulated gene 1; NEFL, neurofilament light polypeptide 68 kDa; PLA2, phospholipase A2; PMP22, peripheral myelin protein 22; PRPS1, phosphoribosylpyrophosphate synthetase I (PRPS1); PRX, periaxin; RAB7, RAS-associated protein RAB7. Figure 71-3  Classification of Charcot–Marie–Tooth Disease.

on a research basis. Specific genetic diagnoses enable evaluation of relatives, prognostication and prediction of recurrence risk, and antenatal testing. Classification and clinical assessment are complicated by the fact that a single phenotype is often caused by different genes, and that mutations in a gene may present with a variety of phenotypes (see Fig. 71-3). Testing for neuropathies associated with inborn errors of metabolism is based on the clinical and neurophysiologic phenotype. Careful attention needs to be paid to other clinical findings that may guide diagnosis, such as cognitive deficits, vision or hearing loss, evidence of other organ dys­ function, and abnormalities on neuroimaging and biochemical investigations.

CLASSIFICATION OF CMT CMT Type 1 Autosomal dominant demyelinating CMT—CMT type 1—is the most common form of CMT in most populations. Five genes for CMT1 are known (Table 71-2). Most patients present with the “classical” CMT phenotype in the first two decades of life, with a steppage gait, frequent falls, and development of pes cavus. Distal sensory loss is generally mild. There is marked slowing of motor conduction (